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Brudzynski, Stefan M., Michael Wu, and Gordon J. Mogenson. "Decreases in rat locomotor activity as a result of changes in synaptic transmission to neurons within the mesencephalic locomotor region." Canadian Journal of Physiology and Pharmacology 71, no. 5-6 (May 1, 1993): 394–406. http://dx.doi.org/10.1139/y93-060.
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The mesencephalic locomotor region is defined as a functional region sending signals to the spinal cord generators of rhythmical limb movements for locomotion. It has been shown that the mesencephalic locomotor region plays a critical role in locomotion initiated from the nucleus accumbens or from the subpallidal region. However, there are conflicting data on whether synaptic input from the nucleus accumbens – subpallidal region to the mesencephalic locomotor region mediates locomotion. The purpose of the study was to determine the role of synaptic input to different subregions of the mesencephalic locomotor region in locomotion induced by injecting dopamine into the nucleus accumbens or by injecting picrotoxin into the subpallidal region in freely behaving rats. Synaptic transmission in the mesencephalic locomotor region was eliminated by excitotoxic lesions or was reversibly interrupted by injecting cobalt chloride, which can block synaptic transmission. Excitotoxic lesions or injections of cobalt into subregions of the mesencephalic locomotor region significantly decreased, although did not completely block, locomotion. The most effective sites for cobalt- and lesion-induced reduction in locomotion were consistent with localization of the mesencephalic locomotor region. Effective sites for cobalt and lesions markedly overlapped but were not identical. The results indicate that synaptic transmission within the mesencephalic locomotor region contributes to dopamine- or picrotoxin-induced locomotion.Key words: locomotion, mesencephalic locomotor region, nucleus accumbens, ventral pallidum, dopamine, picrotoxin, excitotoxins, cobalt chloride.
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Gerasimenko, Yury, Chet Preston, Hui Zhong, Roland R. Roy, V. Reggie Edgerton, and Prithvi K. Shah. "Rostral lumbar segments are the key controllers of hindlimb locomotor rhythmicity in the adult spinal rat." Journal of Neurophysiology 122, no. 2 (August 1, 2019): 585–600. http://dx.doi.org/10.1152/jn.00810.2018.
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The precise location and functional organization of the spinal neuronal locomotor-related networks in adult mammals remain unclear. Our recent neurophysiological findings provided empirical evidence that the rostral lumbar spinal cord segments play a critical role in the initiation and generation of the rhythmic activation patterns necessary for hindlimb locomotion in adult spinal rats. Since added epidural stimulation at the S1 segments significantly enhanced the motor output generated by L2 stimulation, these data also suggested that the sacral spinal cord provides a strong facilitory influence in rhythm initiation and generation. However, whether L2 will initiate hindlimb locomotion in the absence of S1 segments, and whether S1 segments can facilitate locomotion in the absence of L2 segments remain unknown. Herein, adult rats received complete spinal cord transections at T8 and then at either L2 or S1. Rats with spinal cord transections at T8 and S1 remained capable of generating coordinated hindlimb locomotion when receiving epidural stimulation at L2 and when ensembles of locomotor related loadbearing input were present. In contrast, minimal locomotion was observed when S1 stimulation was delivered after spinal cord transections at T8 and L2. Results were similar when the nonspecific serotonergic agonists were administered. These results demonstrate in adult rats that rostral lumbar segments are essential for the regulation of hindlimb locomotor rhythmicity. In addition, the more caudal spinal networks alone cannot control locomotion in the absence of the rostral segments around L2 even when loadbearing rhythmic proprioceptive afferent input is imposed. NEW & NOTEWORTHY The exact location of the spinal neuronal locomotor-related networks in adult mammals remains unknown. The present data demonstrate that when the rostral lumbar spinal segments (~L2) are completely eliminated in thoracic spinal adult rats, hindlimb stepping is not possible with neurochemical modulation of the lumbosacral cord. In contrast, eliminating the sacral cord retains stepping ability. These observations highlight the importance of rostral lumbar segments in generating effective mammalian locomotion.
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Liu, Jun, and Larry M. Jordan. "Stimulation of the Parapyramidal Region of the Neonatal Rat Brain Stem Produces Locomotor-Like Activity Involving Spinal 5-HT7 and 5-HT2A Receptors." Journal of Neurophysiology 94, no. 2 (August 2005): 1392–404. http://dx.doi.org/10.1152/jn.00136.2005.
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Locomotion can be induced in rodents by direct application 5-hydroxytryptamine (5-HT) onto the spinal cord. Previous studies suggest important roles for 5-HT7 and 5-HT2A receptors in the locomotor effects of 5-HT. Here we show for the first time that activation of a discrete population of 5-HT neurons in the rodent brain stem produces locomotion and that the evoked locomotion requires 5-HT7 and 5-HT2A receptors. Cells localized in the parapyramidal region (PPR) of the mid-medulla produced locomotor-like activity as a result of either electrical or chemical stimulation, and PPR-evoked locomotor-like activity was blocked by antagonists to 5-HT2A and 5-HT7 receptors located on separate populations of neurons concentrated in different rostro-caudal regions. 5-HT7 receptor antagonists blocked locomotor-like activity when applied above the L3 segment; 5-HT2A receptor antagonists blocked locomotor-like activity only when applied below the L2 segment. 5-HT7 receptor antagonists decreased step cycle duration, consistent with an action on neurons involved in the rhythm-generating function of the central pattern generator (CPG) for locomotion. 5-HT2A antagonists reduced the amplitude of ventral root activity with only small effects on step cycle duration, suggesting an action directly on cells involved in the output stage of the pattern generator for locomotion, including motoneurons and premotor cells. Experiments with selective antagonists show that dopaminergic (D1, D2) and noradrenergic (α1, α2) receptors are not critical for PPR-evoked locomotor-like activity.
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Tresch, Matthew C., and Ole Kiehn. "Population Reconstruction of the Locomotor Cycle From Interneuron Activity in the Mammalian Spinal Cord." Journal of Neurophysiology 83, no. 4 (April 1, 2000): 1972–78. http://dx.doi.org/10.1152/jn.2000.83.4.1972.
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Lesion studies have shown that neuronal networks in the ventromedial regions of the neonatal rat spinal cord are critical for the production of locomotion. We examined whether the locomotor cycle could be accurately predicted based on the activity recorded in a population of spinal interneurons located in these regions during pharmacologically induced locomotion. We used a Bayesian probabilistic reconstruction procedure to predict the most likely phase of locomotion given the observed activity in the neuronal population. The population reconstruction was able to predict the correct locomotor phase with high accuracy using a relatively small number of neurons. This result demonstrates that although the spike activity of individual spinal interneurons in the ventromedial region is weak and varies from cycle to cycle, the locomotor phase can be accurately predicted when information from the population is combined. This result is consistent with the proposed involvement of interneurons within these regions of the spinal cord in the production of locomotion.
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Hayes, Heather Brant, Young-Hui Chang, and Shawn Hochman. "An In Vitro Spinal Cord–Hindlimb Preparation for Studying Behaviorally Relevant Rat Locomotor Function." Journal of Neurophysiology 101, no. 2 (February 2009): 1114–22. http://dx.doi.org/10.1152/jn.90523.2008.
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Although the spinal cord contains the pattern-generating circuitry for producing locomotion, sensory feedback reinforces and refines the spatiotemporal features of motor output to match environmental demands. In vitro preparations, such as the isolated rodent spinal cord, offer many advantages for investigating locomotor circuitry, but they lack the natural afferent feedback provided by ongoing locomotor movements. We developed a novel preparation consisting of an isolated in vitro neonatal rat spinal cord oriented dorsal-up with intact hindlimbs free to step on a custom-built treadmill. This preparation combines the neural accessibility of in vitro preparations with the modulatory influence of sensory feedback from physiological hindlimb movement. Locomotion induced by N-methyl d-aspartate and serotonin showed kinematics similar to that of normal adult rat locomotion. Changing orientation and ground interaction (dorsal-up locomotion vs ventral-up air-stepping) resulted in significant kinematic and electromyographic changes that were comparable to those reported under similar mechanical conditions in vivo. We then used two mechanosensory perturbations to demonstrate the influence of sensory feedback on in vitro motor output patterns. First, swing assistive forces induced more regular, robust muscle activation patterns. Second, altering treadmill speed induced corresponding changes in stride frequency, confirming that changes in sensory feedback can alter stride timing in vitro. In summary, intact hindlimbs in vitro can generate behaviorally appropriate locomotor kinematics and responses to sensory perturbations. Future studies combining the neural and chemical accessibility of the in vitro spinal cord with the influence of behaviorally appropriate hindlimb movements will provide further insight into the operation of spinal motor pattern-generating circuits.
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Bedford, T. G., P. K. Loi, and C. C. Crandall. "A model of dynamic exercise: the decerebrate rat locomotor preparation." Journal of Applied Physiology 72, no. 1 (January 1, 1992): 121–27. http://dx.doi.org/10.1152/jappl.1992.72.1.121.
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The purpose of this study was to develop a dynamic exercise model in the rat that could be used to study central nervous system control of the cardiovascular system. Rats of both sexes were decerebrated under halothane anesthesia and prepared for induced locomotion on a freely turning wheel. Electrical stimulation of the mesencephalic locomotor region (MLR) elicited locomotion at different speeds and gait patterns and increased heart rate and blood pressure. Two maneuvers were performed to illustrate the potential use of the preparation. The first maneuver consisted of muscular paralysis, which prevents excitation of muscle mechanoreceptors and chemoreceptors resulting from exercise. MLR stimulation still increased blood pressure. The second maneuver was performed to determine whether the blood pressure response obtained during paralysis was an artifact of electrical stimulation of the MLR. After microinjection of gamma-aminobutyric acid into the MLR, electrical current thresholds for blood pressure and locomotion increased in parallel. gamma-Aminobutyric acid injection also reduced the pressor response to suprathreshold electrical stimulation by 76%. The injection results suggest that electrical stimulation of the MLR activates cells rather than fibers of passage. The blood pressure response of the exercise model is probably not an artifact of stimulation. The decerebrate rat locomotor preparation should offer another approach to investigate difficult problems in exercise physiology.
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Ballion, Bérangère, Didier Morin, and Denise Viala. "Forelimb locomotor generators and quadrupedal locomotion in the neonatal rat." European Journal of Neuroscience 14, no. 10 (November 2001): 1727–38. http://dx.doi.org/10.1046/j.0953-816x.2001.01794.x.
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Sławińska, Urszula, Henryk Majczyński, Anna Kwaśniewska, Krzysztof Miazga, Anna M. Cabaj, Marek Bekisz, Larry M. Jordan, and Małgorzata Zawadzka. "Unusual Quadrupedal Locomotion in Rat during Recovery from Lumbar Spinal Blockade of 5-HT7 Receptors." International Journal of Molecular Sciences 22, no. 11 (June 2, 2021): 6007. http://dx.doi.org/10.3390/ijms22116007.
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Coordination of four-limb movements during quadrupedal locomotion is controlled by supraspinal monoaminergic descending pathways, among which serotoninergic ones play a crucial role. Here we investigated the locomotor pattern during recovery from blockade of 5-HT7 or 5-HT2A receptors after intrathecal application of SB269970 or cyproheptadine in adult rats with chronic intrathecal cannula implanted in the lumbar spinal cord. The interlimb coordination was investigated based on electromyographic activity recorded from selected fore- and hindlimb muscles during rat locomotion on a treadmill. In the time of recovery after hindlimb transient paralysis, we noticed a presence of an unusual pattern of quadrupedal locomotion characterized by a doubling of forelimb stepping in relation to unaffected hindlimb stepping (2FL-1HL) after blockade of 5-HT7 receptors but not after blockade of 5-HT2A receptors. The 2FL-1HL pattern, although transient, was observed as a stable form of fore-hindlimb coupling during quadrupedal locomotion. We suggest that modulation of the 5-HT7 receptors on interneurons located in lamina VII with ascending projections to the forelimb spinal network can be responsible for the 2FL-1HL locomotor pattern. In support, our immunohistochemical analysis of the lumbar spinal cord demonstrated the presence of the 5-HT7 immunoreactive cells in the lamina VII, which were rarely 5-HT2A immunoreactive.
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Bauman, Jay M., and Young-Hui Chang. "Rules to limp by: joint compensation conserves limb function after peripheral nerve injury." Biology Letters 9, no. 5 (October 23, 2013): 20130484. http://dx.doi.org/10.1098/rsbl.2013.0484.
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Locomotion persists across all manner of internal and external perturbations. The objective of this study was to identify locomotor compensation strategies in rodent models of peripheral nerve injury. We found that hip-to-toe limb length and limb angle was preferentially preserved over individual joint angles after permanent denervation of rat ankle extensor muscles. These findings promote further enquiry into the significance of limb-level function for neuromechanical control of legged locomotion.
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Ettema, G. J. "Elastic and length-force characteristics of the gastrocnemius of the hopping mouse (Notomys alexis) and the rat (Rattus norvegicus)." Journal of Experimental Biology 199, no. 6 (June 1, 1996): 1277–85. http://dx.doi.org/10.1242/jeb.199.6.1277.
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The aim of this study was to compare the contractile and series elastic properties of terrestrial mammals that use bipedal versus quadrupedal gaits. The gastrocnemius muscle of the hopping mouse (body mass 30.2 +/- 2.4 g, mean +/- S.D.) and the rat (313 +/- 10.7 g) were compared with data from the literature for the wallaby and the kangaroo rat to distinguish scaling effects and locomotion-related effects on muscle properties. Contractile length-force properties and series elastic stiffness were measured in situ during maximal tetanic contractions. The rat had a larger muscle-fibre-to-tendon-length ratio. The rat and hopping mouse showed similar normalised length-force characteristics of the gastrocnemius. Normalised stiffness in the hopping mouse was higher. The hopping mouse showed a higher capacity to store elastic energy per unit of contractile work capacity, as well as per unit of body mass. Accounting for body size differences, the rat had a smaller relative muscle mass and thus smaller work capacity than the three hopping animals considered. This is an agreement with a quadrupedal versus bipedal locomotion style. The differences in contractile and elastic properties of the gastrocnemius of the rat and hopping mouse seem to be closely related to locomotion patterns. Small animals seem to be able to utilise the storage and release of elastic energy to a far lesser extent than larger animals. However, even in animals as small as hopping mice, the storage and utilisation of elastic energy during locomotion is of functional significance and probably depends on locomotor behaviour.
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Parker, Andrew J., and Kenneth A. Clarke. "Gait topography in rat locomotion." Physiology & Behavior 48, no. 1 (July 1990): 41–47. http://dx.doi.org/10.1016/0031-9384(90)90258-6.
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Atsuta, Y., E. Garcia-Rill, and R. D. Skinner. "Characteristics of electrically induced locomotion in rat in vitro brain stem-spinal cord preparation." Journal of Neurophysiology 64, no. 3 (September 1, 1990): 727–35. http://dx.doi.org/10.1152/jn.1990.64.3.727.
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1. Electrical stimulation of two brain stem regions in the decerebrate neonatal rat brain--the mesencephalic locomotor region (MLR) and the medioventral medulla (MED)--were found to elicit rhythmic limb movements in the hind-limb-attached, in vitro, brain stem-spinal cord preparation. 2. Electromyographic (EMG) analysis revealed locomotion similar to that observed during stepping in the adult rat. The step-cycle frequency could be increased by application of higher-amplitude currents; but, unlike the adult, alternation could not be driven to a gallop. 3. Threshold currents for inducing locomotion were significantly lower for stimulation of the MED compared with the MLR. Brain stem transections carried out at midpontine levels demonstrated that the presence of the MLR was not required for the expression of MED-stimulation-induced effects. 4. Substitution of the standard artificial cerebrospinal fluid (aCSF) by magnesium-free aCSF did not affect interlimb relationships and resulted in a significant decrease of the threshold currents for inducing locomotion. 5. Fixation of the limbs during electrical stimulation of brain stem sites altered the amplitude and duration of the EMG patterns, but the basic rhythm and timing of each muscle contraction during the step cycle was not affected. 6. These studies suggest that, although peripheral afferent modulation is evident in the neonatal locomotor control system, descending projections from brain stem-locomotor regions appear capable of modulating the activity of spinal pattern generators as early as the day of birth. However, there may be ceiling to the maximal frequency of stepping possible at this early age, perhaps suggesting a later-developing mechanism for galloping.
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Heiland, B., and S. A. Greenfield. "Rat Locomotion and Release of Acetylcholinesterase." Pharmacology Biochemistry and Behavior 62, no. 1 (January 1999): 81–87. http://dx.doi.org/10.1016/s0091-3057(98)00117-8.
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Fish, F. E., and R. V. Baudinette. "Energetics of locomotion by the Australian water rat (Hydromys chrysogaster): a comparison of swimming and running in a semi-aquatic mammal." Journal of Experimental Biology 202, no. 4 (February 15, 1999): 353–63. http://dx.doi.org/10.1242/jeb.202.4.353.
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Semi-aquatic mammals occupy a precarious evolutionary position, having to function in both aquatic and terrestrial environments without specializing in locomotor performance in either environment. To examine possible energetic constraints on semi-aquatic mammals, we compared rates of oxygen consumption for the Australian water rat (Hydromys chrysogaster) using different locomotor behaviors: swimming and running. Aquatic locomotion was investigated as animals swam in a water flume at several speeds, whereas water rats were run on a treadmill to measure metabolic effort during terrestrial locomotion. Water rats swam at the surface using alternate pelvic paddling and locomoted on the treadmill using gaits that included walk, trot and half-bound. Water rats were able to run at twice their maximum swimming velocity. Swimming metabolic rate increased with velocity in a pattern similar to the ‘humps’ and ‘hollows’ for wave drag experienced by bodies moving at the water surface. Metabolic rate increased linearly during running. Over equivalent velocities, the metabolic rate for running was 13–40 % greater than for swimming. The minimum cost of transport for swimming (2.61 J N-1 m-1) was equivalent to values for other semi-aquatic mammals. The lowest cost for running (2.08 J N-1 m-1) was 20 % lower than for swimming. When compared with specialists at the extremes of the terrestrial-aquatic continuum, the energetic costs of locomoting either in water or on land were high for the semi-aquatic Hydromys chrysogaster. However, the relative costs for H. chrysogaster were lower than when an aquatic specialist attempts to move on land or a terrestrial specialist attempts to swim.
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Alluin, Olivier, Hugo Delivet-Mongrain, and Serge Rossignol. "Inducing hindlimb locomotor recovery in adult rat after complete thoracic spinal cord section using repeated treadmill training with perineal stimulation only." Journal of Neurophysiology 114, no. 3 (September 2015): 1931–46. http://dx.doi.org/10.1152/jn.00416.2015.
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Although a complete thoracic spinal cord section in various mammals induces paralysis of voluntary movements, the spinal lumbosacral circuitry below the lesion retains its ability to generate hindlimb locomotion. This important capacity may contribute to the overall locomotor recovery after partial spinal cord injury (SCI). In rats, it is usually triggered by pharmacological and/or electrical stimulation of the cord while a robot sustains the animals in an upright posture. In the present study we daily trained a group of adult spinal (T7) rats to walk with the hindlimbs for 10 wk (10 min/day for 5 days/wk), using only perineal stimulation. Kinematic analysis and terminal electromyographic recordings revealed a strong effect of training on the reexpression of hindlimb locomotion. Indeed, trained animals gradually improved their locomotion while untrained animals worsened throughout the post-SCI period. Kinematic parameters such as averaged and instant swing phase velocity, step cycle variability, foot drag duration, off period duration, and relationship between the swing features returned to normal values only in trained animals. The present results clearly demonstrate that treadmill training alone, in a normal horizontal posture, elicited by noninvasive perineal stimulation is sufficient to induce a persistent hindlimb locomotor recovery without the need for more complex strategies. This provides a baseline level that should be clearly surpassed if additional locomotor-enabling procedures are added. Moreover, it has a clinical value since intrinsic spinal reorganization induced by training should contribute to improve locomotor recovery together with afferent feedback and supraspinal modifications in patients with incomplete SCI.
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Thota, Anil K., Sonia Carlson Watson, Elizabeth Knapp, Brian Thompson, and Ranu Jung. "Neuromechanical Control of Locomotion in the Rat." Journal of Neurotrauma 22, no. 4 (April 2005): 442–65. http://dx.doi.org/10.1089/neu.2005.22.442.
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Westerga, J., and A. Gramsbergen. "The development of locomotion in the rat." Developmental Brain Research 57, no. 2 (December 1990): 163–74. http://dx.doi.org/10.1016/0165-3806(90)90042-w.
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Canu, M. H., and M. Falempin. "Effect of hindlimb unloading on locomotor strategy during treadmill locomotion in the rat." European Journal of Applied Physiology 74, no. 4 (October 1, 1996): 297–304. http://dx.doi.org/10.1007/s004210050078.
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Canu, M. H., and M. Falempin. "Effect of hindlimb unloading on locomotor strategy during treadmill locomotion in the rat." European Journal of Applied Physiology and Occupational Physiology 74, no. 4 (October 1996): 297–304. http://dx.doi.org/10.1007/bf02226924.
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Rossignol, Serge. "Plasticity of connections underlying locomotor recovery after central and/or peripheral lesions in the adult mammals." Philosophical Transactions of the Royal Society B: Biological Sciences 361, no. 1473 (August 4, 2006): 1647–71. http://dx.doi.org/10.1098/rstb.2006.1889.
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This review discusses some aspects of plasticity of connections after spinal injury in adult animal models as a basis for functional recovery of locomotion. After reviewing some pitfalls that must be avoided when claiming functional recovery and the importance of a conceptual framework for the control of locomotion, locomotor recovery after spinal lesions, mainly in cats, is summarized. It is concluded that recovery is partly due to plastic changes within the existing spinal locomotor networks. Locomotor training appears to change the excitability of simple reflex pathways as well as more complex circuitry. The spinal cord possesses an intrinsic capacity to adapt to lesions of central tracts or peripheral nerves but, as a rule, adaptation to lesions entails changes at both spinal and supraspinal levels. A brief summary of the spinal capacity of the rat, mouse and human to express spinal locomotor patterns is given, indicating that the concepts derived mainly from work in the cat extend to other adult mammals. It is hoped that some of the issues presented will help to evaluate how plasticity of existing connections may combine with and potentiate treatments designed to promote regeneration to optimize remaining motor functions.
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Tresch, Matthew C., and Ole Kiehn. "Coding of Locomotor Phase in Populations of Neurons in Rostral and Caudal Segments of the Neonatal Rat Lumbar Spinal Cord." Journal of Neurophysiology 82, no. 6 (December 1, 1999): 3563–74. http://dx.doi.org/10.1152/jn.1999.82.6.3563.
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Several experiments have demonstrated that rostral segments of the vertebrate lumbar spinal cord produce a rhythmic motor output more readily and of better quality than caudal segments. Here we examine how this rostrocaudal gradient of rhythmogenic capability is reflected in the spike activity of neurons in the rostral (L2) and caudal (L5) lumbar spinal cord of the neonatal rat. The spike activity of interneurons in the ventromedial cord, a region necessary for the production of locomotion, was recorded intracellularly with patch electrodes and extracellularly with tetrodes during pharmacologically induced locomotion. Both L2 and L5 neurons tended to be active in phase with their homologous ventral root. L5 neurons, however, had a wider distribution of their preferred phases of activity throughout the locomotor cycle than L2 neurons. The strength of modulation of the activity of individual L2 neurons was also larger than that of L5 neurons. These differences resulted in a stronger rhythmic signal from the L2 neuronal population than from the L5 population. These results demonstrate that the rhythmogenic capability of each spinal segment was reflected in the activity of interneurons located in the same segment. In addition to paralleling the rostrocaudal gradient of rhythmogenic capability, these results further suggest a colocalization of motoneurons and their associated interneurons involved in the production of locomotion.
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Dunlevy, J. R., and J. R. Couchman. "Controlled induction of focal adhesion disassembly and migration in primary fibroblasts." Journal of Cell Science 105, no. 2 (June 1, 1993): 489–500. http://dx.doi.org/10.1242/jcs.105.2.489.
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Fibroblast migration is an integral component of biological processes such as wound healing and embryogenesis. Previous experiments examining fibroblast locomotion from tissue explants have shown that migrating fibroblasts lack, or contain only transient, focal adhesions (focal contacts). Focal adhesions are specialized regions of tight cell-matrix interaction, assembled by a complex process of transmembrane signalling. Although the explant model has been used for studying several aspects of fibroblast locomotion, it is limited by the lack of control over migration, and only a small percentage of the cells actually locomoting. Therefore, we have developed an in vitro model for cultured fibroblast strains where the presence or absence of focal adhesions can be manipulated, and in the latter case 70% of these cells become locomotory. The stimulus used to decrease the percentage of cells containing focal adhesions, and hence enhance locomotion, was newborn rat heart-conditioned medium (HCM). Addition of HCM to rat embryo fibroblasts induced both chemokinesis and chemotaxis. Cells disassembled focal adhesions on a variety of extracellular matrix substrates after approximately 6 h of stimulation with HCM; conversely, removal of HCM promoted reformation of focal adhesions within 12–24 h. HCM-stimulated fibroblasts which lacked focal adhesions concomitantly lacked F-actin stress fibers and focal concentrations of vinculin and talin. Therefore, fibroblast migration can be readily controlled in an on-off manner through conditioned medium, which influences the absence or presence of focal adhesions.
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Dose, Francesco, and Giuliano Taccola. "Coapplication of noisy patterned electrical stimuli and NMDA plus serotonin facilitates fictive locomotion in the rat spinal cord." Journal of Neurophysiology 108, no. 11 (December 1, 2012): 2977–90. http://dx.doi.org/10.1152/jn.00554.2012.
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A new stimulating protocol [fictive locomotion-induced stimulation (FL istim)], consisting of intrinsically variable weak waveforms applied to a single dorsal root is very effective (though not optimal as it eventually wanes away) in activating the locomotor program of the isolated rat spinal cord. The present study explored whether combination of FL istim with low doses of pharmacological agents that raise network excitability might further improve the functional outcome, using this in vitro model. FL istim was applied together with N-methyl-d-aspartate (NMDA) + serotonin, while fictive locomotion (FL) was electrophysiologically recorded from lumbar ventral roots. Superimposing FL istim on FL evoked by these neurochemicals persistently accelerated locomotor-like cycles to a set periodicity and modulated cycle amplitude depending on FL istim rate. Trains of stereotyped rectangular pulses failed to replicate this phenomenon. The GABAB agonist baclofen dose dependently inhibited, in a reversible fashion, FL evoked by either FL istim or square pulses. Sustained episodes of FL emerged when FL istim was delivered, at an intensity subthreshold for FL, in conjunction with subthreshold pharmacological stimulation. Such an effect was, however, not found when high potassium solution instead of NMDA + serotonin was used. These results suggest that the combined action of subthreshold FL istim (e.g., via epidural stimulation) and neurochemicals should be tested in vivo to improve locomotor rehabilitation after injury. In fact, reactivation of spinal locomotor circuits by conventional electrical stimulation of afferent fibers is difficult, while pharmacological activation of spinal networks is clinically impracticable due to concurrent unwanted effects. We speculate that associating subthreshold chemical and electrical inputs might decrease side effects when attempting to evoke human locomotor patterns.
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Armstrong, R. B., R. Phelps, K. Rouk, R. Stroup, J. White, and M. H. Laughlin. "RAT MUSCLE BLOOD FLOWS DURING HIGH SPEED LOCOMOTION." Medicine & Science in Sports & Exercise 17, no. 2 (April 1985): 282. http://dx.doi.org/10.1249/00005768-198504000-00449.
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Rigosa, J., A. Panarese, N. Dominici, L. Friedli, R. van den Brand, J. Carpaneto, J. DiGiovanna, G. Courtine, and S. Micera. "Decoding bipedal locomotion from the rat sensorimotor cortex." Journal of Neural Engineering 12, no. 5 (September 2, 2015): 056014. http://dx.doi.org/10.1088/1741-2560/12/5/056014.
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Armstrong, R. B., and M. H. Laughlin. "Rat muscle blood flows during high-speed locomotion." Journal of Applied Physiology 59, no. 4 (October 1, 1985): 1322–28. http://dx.doi.org/10.1152/jappl.1985.59.4.1322.
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We previously studied blood flow distribution within and among rat muscles as a function of speed from walking (15 m/min) through galloping (75 m/min) on a motor-driven treadmill. The results showed that muscle blood flows continued to increase as a function of speed through 75 m/min. The purpose of the present study was to have rats run up to maximal treadmill speeds to determine if blood flows in the muscles reach a plateau as a function of running speed over the animals' normal range of locomotory speeds. Muscle blood flows were measured with radiolabeled microspheres at 1 min of running at 75, 90, and 105 m/min in male Sprague-Dawley rats. The data indicate that even at these relatively high treadmill speeds there was still no clear evidence of a plateau in blood flow in most of the hindlimb muscles. Flows in most muscles continued to increase as a function of speed. These observed patterns of blood flow vs. running speed may have resulted from the rigorous selection of rats that were capable of performing the high-intensity exercise and thus only be representative of a highly specific population of animals. On the other hand, the data could be interpreted to indicate that the cardiovascular potential during exercise is considerably higher in laboratory rats than has normally been assumed and that inadequate blood flow delivery to the muscles does not serve as a major limitation to their locomotory performance.
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Coles, S. K., J. F. Iles, and S. Nicolopoulos-Stournaras. "The mesencephalic centre controlling locomotion in the rat." Neuroscience 28, no. 1 (January 1989): 149–57. http://dx.doi.org/10.1016/0306-4522(89)90239-x.
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Li, Bo, Minjian Zhang, Yafei Liu, Dingyin Hu, Juan Zhao, Rongyu Tang, Yiran Lang, and Jiping He. "Rat Locomotion Detection Based on Brain Functional Directed Connectivity from Implanted Electroencephalography Signals." Brain Sciences 11, no. 3 (March 9, 2021): 345. http://dx.doi.org/10.3390/brainsci11030345.
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Previous findings have suggested that the cortex involved in walking control in freely locomotion rats. Moreover, the spectral characteristics of cortical activity showed significant differences in different walking conditions. However, whether brain connectivity presents a significant difference during rats walking under different behavior conditions has yet to be verified. Similarly, whether brain connectivity can be used in locomotion detection remains unknown. To address those concerns, we recorded locomotion and implanted electroencephalography signals in freely moving rats performing two kinds of task conditions (upslope and downslope walking). The Granger causality method was used to determine brain functional directed connectivity in rats during these processes. Machine learning algorithms were then used to categorize the two walking states, based on functional directed connectivity. We found significant differences in brain functional directed connectivity varied between upslope and downslope walking. Moreover, locomotion detection based on brain connectivity achieved the highest accuracy (91.45%), sensitivity (90.93%), specificity (91.3%), and F1-score (91.43%). Specifically, the classification results indicated that connectivity features in the high gamma band contained the most discriminative information with respect to locomotion detection in rats, with the support vector machine classifier exhibiting the most efficient performance. Our study not only suggests that brain functional directed connectivity in rats showed significant differences in various behavioral contexts but also proposed a method for classifying the locomotion states of rat walking, based on brain functional directed connectivity. These findings elucidate the characteristics of neural information interaction between various cortical areas in freely walking rats.
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Bertrand, Sandrine, and Jean-René Cazalets. "Postinhibitory Rebound During Locomotor-Like Activity in Neonatal Rat Motoneurons In Vitro." Journal of Neurophysiology 79, no. 1 (January 1, 1998): 342–51. http://dx.doi.org/10.1152/jn.1998.79.1.342.
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Bertrand, Sandrine and Jean-René Cazalets. Postinhibitory rebound during locomotor-like activity in neonatal rat motoneurons in vitro. J. Neurophysiol. 79: 342–351, 1998. The aim of this study was to establish how a membrane property contributes to the neuronal discharge during ongoing behavior. We therefore studied the role of the postinhibitory rebound (PIR) in the bursting discharge of lumbar motoneurons intracellularly recorded in newborn rat in vitro brain stem/spinal cord preparation. The PIR is a transient depolarization that occurs after a hyperpolarization. We first investigated how it was expressed during experimentally induced hyperpolarizations. Its amplitude increased with the inhibition and was voltage dependent. The Ca2+ channel blockers Mn2+ and Co2+ partly suppressed the PIR in a few of the motoneurons tested. When hyperpolarized, the motoneurons exhibited a sag that was associated with the PIR. Adding caesium to the bath abolished both sag and rebound, which suggested that the PIR in the lumbar motoneurons was mainly due to the activation of the inward rectifying current I Q. In the second part, we studied the physiological involvement of PIR during fictive locomotion induced by bath application of N-methyl-d-l-aspartate and serotonin. We established that experimentally induced PIR could initiate or modulate the bursting discharge of motoneurons during fictive locomotion. We then studied whether the firing patterns of the motoneurons were correlated in one way with the synaptic inhibition. When the monosynaptic inhibitory input to the motoneurons was abolished with the glycinergic blocker strychnine, these neurons stopped discharging (although they still were depolarized rhythmically). The firing of action potentials was restored by applying negative current pulses. This study provides evidence as to how one membrane property in mammals is involved in a complex type of behavior, namely locomotion.
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West, M. O., R. M. Carelli, M. Pomerantz, S. M. Cohen, J. P. Gardner, J. K. Chapin, and D. J. Woodward. "A region in the dorsolateral striatum of the rat exhibiting single-unit correlations with specific locomotor limb movements." Journal of Neurophysiology 64, no. 4 (October 1, 1990): 1233–46. http://dx.doi.org/10.1152/jn.1990.64.4.1233.
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1. To examine the activity of single units in the lateral striatum of the awake rat with respect to sensorimotor function, 788 units were recorded during locomotion and passive testing. The focus of this report is on 138 units (18%) that fired in relation to sensorimotor activity of a single limb. The remaining units were related to other body parts (16%), to general body movement (38%), or were unresponsive (28%). 2. Firing rates of limb-related units were near zero during resting behavior but increased markedly during treadmill locomotion. Each of the 138 units exhibited a rhythmic pattern of discharge in phase with the locomotor step cycle. Passive testing revealed that 86/97 units tested (89%) responded to passive manipulation of a single limb, exhibiting increased firing rates. Of these, 77 (90%) were related to contralateral and 9 (10%) to ipsilateral limbs. Sixty-one units (71%) were related to a forelimb and 25 (29%) to a hindlimb. Of the 86 units responding to passive manipulation. 34/48 units tested (71%) also responded to cutaneous stimulation of the same limb but no other part of the body. 3. To study in greater detail the rhythmic unit discharges in phase with the locomotor step cycle, computer-synchronized videotape recordings were used to generate perimovement time histograms constructed around discrete locomotor movements of each limb (n = 17 units). Activity of each unit was shown to be restricted to a specific portion of a particular limb's step cycle. The majority of units discharged throughout (8 units) or during a portion of (3 units) the swing phase, whereas other units fired during a portion of stance (3 units), footfall (2 units), or foot off (1 unit). 1. The specificity of unit firing was further demonstrated by the finding that rhythmic discharges, related to discrete locomotor limb movements in the forward direction, were completely absent during spontaneous deviations such as backward or disrupted locomotion. 5. Units related to limb movement were located in the far lateral, especially the dorsolateral, subregion of the striatum. This subregion extend rostrocaudally from A-P +1.6 to -1.0 mm relative to bregma. No clear somatotopic organization was observed, but this issue requires further study. 6. These results show that functional representations of individual limbs can be demonstrated in the lateral striatum of the rat, within a subregion containing terminals of projections from somatic sensorimotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)
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Smith, S. S. "Sensorimotor-correlated discharge recorded from ensembles of cerebellar Purkinje cells varies across the estrous cycle of the rat." Journal of Neurophysiology 74, no. 3 (September 1, 1995): 1095–108. http://dx.doi.org/10.1152/jn.1995.74.3.1095.
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1. In the present study, locomotor-correlated activity of cerebellar Purkinje cells, recorded using arrays of microwires chronically implanted in adult female rats, was examined across estrous-cycle-associated fluctuations in endogenous sex steroids. Ongoing studies from this laboratory have shown that systemic and local administration of the sex steroid 17 beta-estradiol (E2) augments excitatory responses of cerebellar Purkinje cells to iontophoretically applied glutamate, recorded in vivo from anesthetized female rats. In addition, this steroid potentiated discharge correlated with limb movement. For the present study, extracellular single-unit activity was recorded from as many as 5-11 Purkinje cells simultaneously during treadmill locomotion paradigms. Motor modulation of activity was recorded across three to five consecutive estrous cycles from behaviorally identified cohorts of neurons to test the hypothesis that fluctuations in endogenous sex steroids alter motor modulation of Purkinje cell discharge. 2. Locomotor-associated discharge correlated with treadmill locomotion was increased by a mean of 47% on proestrus, when E2 levels are elevated, relative to diestrus 1. These changes in discharge rate during treadmill locomotion were of significantly greater magnitude than corresponding cyclic alterations in discharge during stationary periods. 3. Correlations with the circadian cycle were also significant, because peak levels of locomotor-associated discharge on the night of behavioral estrus, following elevations in circulating E2, were on average 67% greater than corresponding discharge recorded during the light (proestrus). 4. Alterations in the step cycle were also observed across the estrous cycle: significant decreases in the duration of the flexion phase (by 265 ms, P < 0.05) were noted on estrus compared with diestrus. 5. When recorded on estrus, Purkinje cell discharge correlated with the stance or flexion phase of the step cycle was greater in magnitude and preceded the event by an average of 130 ms, compared with values determined on diestrus. 6. On estrus, responses of Purkinje neurons to iontophoretically applied quisqualate were enhanced fourfold after administration of exogenous E2, assessed in urethan-anesthetized female rats. 7. In addition, systemic administration of E2 (30 ng iv) potentiated responses of cerebellar Purkinje cells to electrical stimulation of the forepaw by an average of 150%, recorded in anesthetized female rats. 8. These results are consistent with the hypothesis that elevations in circulating E2 are associated with enhanced discharge of cerebellar Purkinje cells in response to pharmacological or electrical stimuli or associated with locomotor behavior.
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Dourado, Margarida, Helder Cardoso-Cruz, Clara Monteiro, and Vasco Galhardo. "Effect of Motor Impairment on Analgesic Efficacy of Dopamine D2/3 Receptors in a Rat Model of Neuropathy." Journal of Experimental Neuroscience 10 (January 2016): JEN.S36492. http://dx.doi.org/10.4137/jen.s36492.
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Testing the clinical efficacy of drugs that also have important side effects on locomotion needs to be properly designed in order to avoid erroneous identification of positive effects when the evaluation depends on motor-related tests. One such example is the evaluation of analgesic role of drugs that act on dopaminergic receptors, since the pain perception tests used in animal models are based on motor responses that can also be compromised by the same substances. The apparent analgesic effect obtained by modulation of the dopaminergic system is still a highly disputed topic. There is a lack of acceptance of this effect in both preclinical and clinical settings, despite several studies showing that D2/3 agonists induce antinociception. Some authors raised the hypothesis that this antinociceptive effect is enhanced by dopamine-related changes in voluntary initiation of movement. However, the extent to which D2/3 modulation changes locomotion at analgesic effective doses is still an unresolved question. In the present work, we performed a detailed dose-dependent analysis of the changes that D2/3 systemic modulation have on voluntary locomotor activity and response to four separate tests of both thermal and mechanical pain sensitivity in adult rats. Using systemic administration of the dopamine D2/3 receptor agonist quinpirole, and of the D2/3 antagonist raclopride, we found that modulation of D2/3 receptors impairs locomotion and exploratory activity in a dose-dependent manner across the entire range of tested dosages. None of the drugs were able to consistently diminish either thermal or mechanical pain perception when administered at lower concentrations; on the other hand, the larger concentrations of raclopride (0.5–1.0 mg/kg) strongly abolished pain responses, and also caused severe motor impairment. Our results show that administration of both agonists and antagonists of dopaminergic D2/3 receptors affects sensorimotor behaviors, with the effect over locomotion and exploratory activity being stronger than the observed effect over pain responses.
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McMahon, Lance R., and Paul J. Wellman. "PVN infusion of GLP-1-(7—36) amide suppresses feeding but does not induce aversion or alter locomotion in rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 274, no. 1 (January 1, 1998): R23—R29. http://dx.doi.org/10.1152/ajpregu.1998.274.1.r23.
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Intracerebroventricular infusion of glucagon-like peptide-1-(7—36) amide (GLP-1) reduces feeding in rats, an effect that could be localized to the hypothalamic paraventricular nucleus (PVN). Intracerebroventricular GLP-1, however, may also induce conditioned taste aversion (CTA), thereby putting into question the specificity of the action of GLP-1 on feeding. The present experiments evaluated the action of PVN GLP-1 (0, 100, or 200 ng) on induction of CTA, on locomotion, and finally, on feeding and drinking in rats. PVN infusion of GLP-1 (100 or 200 ng) did not support the induction of CTA and did not reliably alter locomotion, but did suppress feeding and drinking. The present study suggests that GLP-1 infusions into the PVN reduce food and water intake without producing illness or disrupting locomotor behavior. These data, in conjunction with reports of increased feeding following antagonism of central GLP-1 receptors, support the notion that endogenous GLP-1, perhaps within the PVN, functions to suppress feeding in the rat.
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Mogensen, J. "Serotonin, locomotion, exploration, and place recall in the rat." Pharmacology Biochemistry and Behavior 75, no. 2 (May 2003): 381–95. http://dx.doi.org/10.1016/s0091-3057(03)00107-2.
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Arkley, Kendra, Robyn A. Grant, Ben Mitchinson, and Tony J. Prescott. "Strategy Change in Vibrissal Active Sensing during Rat Locomotion." Current Biology 24, no. 13 (July 2014): 1507–12. http://dx.doi.org/10.1016/j.cub.2014.05.036.
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Clarke, Kenneth A., and Elizabeth Williams. "Development of locomotion in the rat— Spatiotemporal footfall patterns." Physiology & Behavior 55, no. 1 (January 1994): 151–55. http://dx.doi.org/10.1016/0031-9384(94)90023-x.
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Clarke, Kenneth A., and Andrew J. Parker. "A quantitative study of normal locomotion in the rat." Physiology & Behavior 38, no. 3 (January 1986): 345–51. http://dx.doi.org/10.1016/0031-9384(86)90105-8.
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Gutman, H., D. Risin, B. P. Katz, and N. R. Pellis. "Locomotion through three-dimentional type I rat tail collagen." Journal of Immunological Methods 157, no. 1-2 (January 1993): 175–80. http://dx.doi.org/10.1016/0022-1759(93)90084-k.
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Cowley, Kristine C., Eugene Zaporozhets, Raed A. Joundi, and Brian J. Schmidt. "Contribution of Commissural Projections to Bulbospinal Activation of Locomotion in the In Vitro Neonatal Rat Spinal Cord." Journal of Neurophysiology 101, no. 3 (March 2009): 1171–78. http://dx.doi.org/10.1152/jn.91212.2008.
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Commissural projections are required for left-right coordination during locomotion. However, their role, if any, in rhythm production is unknown. This study uses the neonatal rat in vitro brain stem–spinal cord model to examine the rostrocaudal distribution of locomotor-related commissural projections and study whether commissural connections are needed for the generation of hindlimb rhythmic activity in response to electrical stimulation of the brain stem. Midsagittal lesions were made at a wide range of rostrocaudal levels. Locomotor-like activity persisted in some preparations despite midsagittal lesions extending from C1 to the mid-L1 level or from the conus medullaris to the T12/13 junction. In some preparations, midsagittal lesions throughout the entire spinal cord had no effect on locomotor-like activity if two or three contiguous segments remained intact. Those bridging segments had to include the T13 and/or L1 levels. These observations suggested that commissural projections in the thoracolumbar junction region were critical. However, locomotor-like activity was also elicited in preparations with limited midsagittal lesions focused on the thoracolumbar junction (T12 through L1 or L2 inclusive). In other experiments, locomotor-like activity was evoked by bath-applied 5-hydroxytryptamine (5-HT) and N-methyl-d-aspartate (NMDA). Appropriate side-to-side coordination was observed, even when only one segment remained bilaterally intact. Commissural projections traversing the thoracolumbar junction region were most effective. In combination, these results suggest that locomotor-related commissural projections are redundantly distributed along a bi-directional gradient that centers on the thoracolumbar junction. This commissural system not only provides a robust left-right coordinating mechanism but also supports locomotor rhythm generation in response to brain stem stimulation.
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Yazawa, Itaru, and Seiji Shioda. "Reciprocal functional interactions between the respiration/circulation center, the upper spinal cord, and the trigeminal system." Translational Neuroscience 6, no. 1 (January 1, 2015): 87–102. http://dx.doi.org/10.1515/tnsci-2015-0008.
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AbstractThe interplay of neural discharge patterns involved in “respiration”, “circulation”, “opening movements in the mandible”, and “locomotion” was investigated electrophysiologically in a decerebrate and arterially perfused in situ rat preparation. Sympathetic tone increased with increases in perfusion flow rate. All nerve discharges became clearly organized into discharge episodes of increasing frequency and duration punctuated by quiescent periods as the perfusion flow rate increased at 26ºC. The modulated sympathetic tone at 10× total blood volume/ min activated the forelimb pattern generator and spontaneously generated fictive forelimb movement during discharge episodes. The coupling rhythm of respiration and locomotion during motion occurred at frequency ratios ranges of 1:2 and 1:3. Small increases in systemic pressure were always generated after the initiation of motion. Opening movements in the mandible, occurring during the inspiratory phase at all tested flow rates, were generated in both the inspiratory and expiratory phases during motion. Although the central mechanism for the entrainment of respiratory and locomotor rhythms has not been identified, a spinal-feedback mechanism generating fictive locomotion in the upper spinal cord contributed to generating the opening movement in the mandible in the expiratory phase during motion. The existence of this mechanism implies that there is a reciprocal functional interaction between the brainstem and the spinal cord, whereby the intake and output of air by the lungs is efficiently improved during movement by both nasal and mouth breathing. These results suggest that this reciprocal functional interaction plays an important role in increasing oxygenated blood flow during locomotion.
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Alsalem, Mohammad, Ahmad Altarifi, Mansour Haddad, Belal Azab, Heba Kalbouneh, Amer Imraish, Tareq Saleh, and Khalid El-Salem. "Analgesic Effects and Impairment in Locomotor Activity Induced by Cannabinoid/Opioid Combinations in Rat Models of Chronic Pain." Brain Sciences 10, no. 8 (August 6, 2020): 523. http://dx.doi.org/10.3390/brainsci10080523.
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Both opioids and cannabinoids have well-known antinociceptive effects in different animal models of chronic pain. However, unwanted side effects limit their use. The aim of this study is to evaluate the antinociceptive effect of combining synthetic cannabinoids with subtherapeutic doses of opioids, and to evaluate the effects of these drugs/combinations on rat’s locomotor activity. Intra-plantar injection of Complete Freund’s Adjuvant (CFA) into the left hindpaw and intraperitoneal injection of streptozotocin (STZ) were used to induce inflammatory and diabetic neuropathic pain in adult male Sprague-Dawley rats, respectively. Von Frey filaments were used to assess the antinociceptive effects of opioids (morphine and tramadol) and the synthetic cannabinoids (HU210 and WIN55212) or their combinations on CFA and STZ-induced mechanical allodynia. Open field test was used to evaluate the effect of these drugs or their combinations on locomotion. HU210 and WIN55212 did not produce significant antinociceptive effect on inflammatory pain while only the maximal dose of HU210 (1 mg/kg) was effective in neuropathic pain. Only the maximal doses of morphine (3.2 mg/kg) and tramadol (10 mg/kg) had significant anti-allodynic effects in both models. Tramadol (1 mg/kg) enhanced the antinociceptive effects of WIN55212 but not HU210 in neuropathic pain with no effect on inflammatory pain. However, in open field test, the aforementioned combination did not change tramadol-induced depression of locomotion. Tramadol and WIN55212 combination produces antinociceptive effects in neuropathic but not inflammatory pain at low doses with no additional risk of locomotor impairment, which may be useful in clinical practice.
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Alves, Joseph Andrews, Barbara Ciralli Boerner, and Diego Andrés Laplagne. "Flexible Coupling of Respiration and Vocalizations with Locomotion and Head Movements in the Freely Behaving Rat." Neural Plasticity 2016 (2016): 1–16. http://dx.doi.org/10.1155/2016/4065073.
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Quadrupedal mammals typically synchronize their respiration with body movements during rhythmic locomotion. In the rat, fast respiration is coupled to head movements during sniffing behavior, but whether respiration is entrained by stride dynamics is not known. We recorded intranasal pressure, head acceleration, instantaneous speed, and ultrasonic vocalizations from male and female adult rats while freely behaving in a social environment. We used high-speed video recordings of stride to understand how head acceleration signals relate to locomotion and developed techniques to identify episodes of sniffing, walking, trotting, and galloping from the recorded variables. Quantitative analysis of synchrony between respiration and head acceleration rhythms revealed that respiration and locomotion movements were coordinated but with a weaker coupling than expected from previous work in other mammals. We have recently shown that rats behaving in social settings produce high rates of ultrasonic vocalizations during locomotion bouts. Accordingly, rats emitted vocalizations in over half of the respiratory cycles during fast displacements. We present evidence suggesting that emission of these calls disrupts the entrainment of respiration by stride. The coupling between these two variables is thus flexible, such that it can be overridden by other behavioral demands.
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Roy, R. R., D. L. Hutchison, D. J. Pierotti, J. A. Hodgson, and V. R. Edgerton. "EMG patterns of rat ankle extensors and flexors during treadmill locomotion and swimming." Journal of Applied Physiology 70, no. 6 (June 1, 1991): 2522–29. http://dx.doi.org/10.1152/jappl.1991.70.6.2522.
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Intramuscular electromyography (EMG) was used to determine and compare the recruitment patterns of the rat soleus (Sol), tibialis anterior (TA), and a deep and a superficial portion of the medial gastrocnemius (MG) during treadmill locomotion at various speeds and inclines and during swimming. Raw EMG signals for 10-20 step or stroke cycles were rectified, averaged, and processed to determine cycle period (EMG onset of one cycle to EMG onset of the next cycle), EMG burst duration, and integrated area of the rectified burst (IEMG). Mean EMG per burst was calculated as IEMG/burst duration. IEMG/min was calculated as IEMG times the number of bursts (cycles) per minute. Cycle period and burst duration of the extensors decreased hyperbolically, while the TA burst duration was unchanged, with increased treadmill speed. With increased treadmill speed, IEMG was decreased in the Sol and unchanged in the MG and TA, whereas IEMG/min decreased in the Sol and increased in the MG and TA. An elevation in treadmill incline resulted in an increase in the activation levels of the MG but not in the Sol or TA. These data indicate that the additional power required at increased speeds and/or inclines of treadmill locomotion is derived from the recruitment of the fast extensors, e.g., the MG. The mean cycle period during swimming was similar to that observed during the fastest treadmill locomotion. EMG burst durations and amplitudes, however, were higher in the TA, relatively similar in the MG, and lower in the Sol during swimming than treadmill locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Gramsbergen, Albert. "Posture and Locomotion in the Rat: Independent or Interdependent Development?" Neuroscience & Biobehavioral Reviews 22, no. 4 (March 1998): 547–53. http://dx.doi.org/10.1016/s0149-7634(97)00043-2.
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Delp, Michael D., Changping Duan, Chester A. Ray, and R. B. Armstrong. "Rat hindlimb muscle blood flow during level and downhill locomotion." Journal of Applied Physiology 86, no. 2 (February 1, 1999): 564–68. http://dx.doi.org/10.1152/jappl.1999.86.2.564.
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During eccentrically biased exercise (e.g., downhill locomotion), whole body oxygen consumption and blood lactate concentrations are lower than during level locomotion. These general systemic measurements indicate that muscle metabolism is lower during downhill exercise. This study was designed to test the hypothesis that hindlimb muscle blood flow is correspondingly lower during downhill vs. level exercise. Muscle blood flow (determined by using radioactive microspheres) was measured in rats after 15 min of treadmill exercise at 15 m/min on the level (L, 0°) or downhill (D, −17°). Blood flow to ankle extensor muscles was either lower (e.g., white gastrocnemius muscle: D, 9 ± 2; L, 15 ± 1 ml ⋅ min−1 ⋅ 100 g−1) or not different (e.g., soleus muscle: D, 250 ± 35; L, 230 ± 21 ml ⋅ min−1 ⋅ 100 g−1) in downhill vs. level exercise. In contrast, blood flow to ankle flexor muscles was higher (e.g., extensor digitorum longus muscle: D, 53 ± 5; L, 31 ± 6 ml ⋅ min−1 ⋅ 100 g−1) during downhill vs. level exercise. When individual extensor and flexor muscle flows were summed, total flow to the leg was lower during downhill exercise (D, 3.24 ± 0.08; L, 3.47 ± 0.05 ml/min). These data indicate that muscle blood flow and metabolism are lower during eccentrically biased exercise but are not uniformly reduced in all active muscles; i.e., flows are equivalent in several ankle extensor muscles and higher in ankle flexor muscles.
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Bolton, David A. E., Arthur D. Y. Tse, Mark Ballermann, John E. Misiaszek, and Karim Fouad. "Task specific adaptations in rat locomotion: Runway versus horizontal ladder." Behavioural Brain Research 168, no. 2 (April 2006): 272–79. http://dx.doi.org/10.1016/j.bbr.2005.11.017.
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Biewener, A. A., and R. Blickhan. "Kangaroo rat locomotion: design for elastic energy storage or acceleration?" Journal of Experimental Biology 140, no. 1 (November 1, 1988): 243–55. http://dx.doi.org/10.1242/jeb.140.1.243.
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Mechanical stresses (force/cross-sectional area) acting in muscles, tendons and bones of the hindlimbs of kangaroo rats (Dipodomys spectabilis) were calculated during steady-speed hops and vertical jumps. Stresses were determined from both high-speed cine films (light and X-ray) and force plate recordings, as well as from in vivo tendon force recordings. Stresses in each hindlimb support element during hopping (1.6-3.1 m s-1) were generally only 33% of those acting during jumping (greater than or equal to 40 cm height): ankle extensor muscles, 80 +/− 12 (S.D.) versus 297 +/− 42 kPa; ankle extensor tendons, 7.9 +/− 1.5 versus 32.7 +/− 4.8 MPa; tibia, −29 +/− 5 versus −110 +/− 25 MPa (all values are for hopping versus jumping). The magnitude of stress in each structure during these locomotor activities was similarly matched to the strength of each element, so that a consistent safety factor to failure is achieved for the hindlimb as a whole (1.5-2.0). The large stresses during jumping were correlated with a three-fold increase in ground reaction forces exerted on the ground compared with the fastest steady hopping speeds. We conclude that, for its size, the kangaroo rat has disproportionately large hindlimb muscles, tendons and bones to withstand the large forces associated with rapid acceleration to avoid predation, which limits their ability to store and recover elastic strain energy. Middle ear morphology and behavioural observations of kangaroo rats jumping vertically to avoid predation by owls and rattlesnakes support this view.
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Armstrong, R. B., and C. R. Taylor. "Glycogen loss in rat muscles during locomotion on different inclines." Journal of Experimental Biology 176, no. 1 (March 1, 1993): 135–44. http://dx.doi.org/10.1242/jeb.176.1.135.
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Running downhill causes structural damage in deep slow-twitch extensor muscles of the limbs. Both mechanical and metabolic hypotheses have been proposed to explain the damage. The purpose of this study was to use measurements of glycogen loss in the muscles and metabolic rates of rats running on the level and up and down 16 degrees inclines at 26 m min-1 to try to distinguish between these hypotheses. Glycogen loss in the soleus and medial head to the triceps brachii muscles during running on the three inclines was proportional to whole-animal oxygen consumption, indicating that there were no unusual metabolic demands on these muscles during the downhill exercise. The minimum area of these muscles showing glycogen loss was smaller during downhill than during uphill running. Average forces in the muscles are similar during locomotion on different inclines at the same speed, suggesting that stresses in the active motor units were greater during downhill running. Thus, the results are more consistent with a mechanical than with a metabolic etiology for the muscle injury resulting from downhill running.
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Stackman, Robert W., Matthew L. Tullman, and Jeffrey S. Taube. "Maintenance of Rat Head Direction Cell Firing During Locomotion in the Vertical Plane." Journal of Neurophysiology 83, no. 1 (January 1, 2000): 393–405. http://dx.doi.org/10.1152/jn.2000.83.1.393.
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Previous studies have identified a subset of neurons in the rat anterodorsal thalamus (ADN) that encode head direction (HD) in absolute space and may be involved in navigation. These HD cells discharge selectively when the rat points its head in a specific direction (the preferred firing direction) in the horizontal plane. HD cells are typically recorded during free movement about a single horizontal surface. The current experiment examined how HD cell firing was influenced by 1) locomotion in the vertical plane and 2) locomotion on two different horizontal surfaces separated in height. Rats were trained in a cylindrical enclosure containing a single polarizing cue card attached to the cylinder wall, covering ∼100° of arc. The enclosure contained two horizontal surfaces: the cylinder floor and an annulus around the cylinder top 76 cm above the floor. A 90° vertical mesh ladder that could be affixed at any angular position on the cylinder wall allowed the rats to locomote back and forth between the two horizontal surfaces. Rats were trained to retrieve food pellets on the cylinder floor as well as climb the mesh ladder to retrieve food pellets on the annulus. HD cell activity was monitored as the rat traversed the horizontal and vertical surfaces of the apparatus. When the angular position of the mesh corresponded to the cell's preferred firing direction, the HD cells maintained their peak discharge rate as the rat climbed up the mesh, but did not fire when the rat climbed down the mesh. In contrast, when the mesh was positioned 180° opposite the preferred firing direction, HD cells did not fire when the rat climbed up the mesh, but exhibited maximal firing when the rat climbed down the mesh. When the mesh was placed 90 or 270° from the preferred firing direction, HD cells exhibited background firing rates during climbing up or down the mesh. While preferred firing directions were maintained between the two horizontal surfaces, peak firing rate increased significantly (∼30%) on the annulus as compared with the cylinder floor. These data demonstrate that HD cells continue to discharge in the vertical plane if the vertical locomotion began with the rat's orientation corresponding to the preferred firing direction. One model consistent with these data are that HD cells define the horizontal reference frame as the animal's plane of locomotion. Further, we propose that HD cell firing, as viewed within a three-dimensional coordinate system, can be characterized as the surface of a hemitorus.
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Gorassini, Monica, Torsten Eken, David J. Bennett, Ole Kiehn, and Hans Hultborn. "Activity of Hindlimb Motor Units During Locomotion in the Conscious Rat." Journal of Neurophysiology 83, no. 4 (April 1, 2000): 2002–11. http://dx.doi.org/10.1152/jn.2000.83.4.2002.
Full textAbstract:
This paper compares the activity of hindlimb motor units from muscles mainly composed of fast-twitch muscle fibers (medial and lateral gastrocnemius: MG/LG, tibialis anterior: TA) to motor units from a muscle mainly composed of slow-twitch muscle fibers (soleus: SOL) during unrestrained walking in the conscious rat. Several differences in the activation profiles of motor units from these two groups of muscles were observed. For example, motor units from fast muscles (e.g., MG/LG and TA) fired at very high mean frequencies of discharge, ranging from 60 to 100 Hz, and almost always were recruited with initial doublets or triplets, i.e., initial frequencies ≥100 Hz. In contrast, the majority of SOL units fired at much lower mean rates of discharge, ≈30 Hz, and had initial frequencies of only 30–60 Hz (i.e., there were no initial doublets/triplets ≥100 Hz). Thus the presence of initial doublet or triplets was dependent on the intrinsic properties of the motor unit, i.e., faster units were recruited with a doublet/triplet more often than slower units. Moreover, in contrast to units from the slow SOL muscle, the activity of single motor units from the fast MG/LG muscle, especially units recruited midway or near the end of a locomotor burst, was unrelated to the activity of the remainder of the motoneuron pool, as measured by the corresponding gross-electromyographic (EMG) signal. This dissociation of activity was suggested to arise from a compartmentalized recruitment of the MG/LG motoneuron pool by the rhythm-generating networks of the spinal cord. In contrast, when comparing the rate modulation of simultaneously recorded motor units within a single LG muscle compartment, the frequency profiles of unit pairs were modulated in a parallel fashion. This suggested that the parent motoneurons were responsive to changes in synaptic inputs during unrestrained walking, unlike the poor rate modulation that occurs during locomotion induced from brain stem stimulation. In summary, data from this study provide evidence that the firing behavior of motor units during unrestrained walking is influenced by both the intrinsic properties of the parent motoneuron and by synaptic inputs from the locomotor networks of the spinal cord. In addition, it also provides the first extensive description of motor-unit activity from different muscles during unrestrained walking in the conscious rat.