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Journal articles on the topic 'Photic entrainment'

Author: Grafiati

Published: 28 June 2021

Last updated: 1 February 2022

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1

Zordan, Mauro, Nicolo' Osterwalder, Ezio Rosato, and Rodolfo Costa. "Extra Ocular Photic Entrainment inDrosophila Melanogaster." Journal of Neurogenetics 15, no. 2 (January 2001): 97–116. http://dx.doi.org/10.3109/01677060109066197.

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2

Rea, Michael A. "Photic Entrainment of Orcadian Rhythms in rodents." Chronobiology International 15, no. 5 (January 1998): 395–423. http://dx.doi.org/10.3109/07420529808998699.

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3

Pieters, Roger, and Gregory A. Lawrence. "Plunging inflows and the summer photic zone in reservoirs." Water Quality Research Journal 47, no. 3-4 (August 1, 2012): 268–75. http://dx.doi.org/10.2166/wqrjc.2012.143.

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Kinbasket and Revelstoke Reservoirs are part of the Columbia River system in eastern British Columbia, Canada. Hydroelectricity from these large reservoirs represents about 30% of the province's generation capacity. Of interest to water use planning is the effect of reservoir operation on pelagic productivity. We address one small part of this question, namely, the supply of nutrients carried by inflows that plunge below the photic zone during the summer. Using an idealized water balance for the photic zone, three cases are considered: (1) a shallow outlet, (2) a deep outlet, and (3) no outflow. For a shallow outlet, all inflow that plunges below the photic zone is upwelled into the photic zone on its way to the outlet. For a deep outlet, inflow that plunges below the photic zone will short circuit or pass directly to the outlet unless entrainment generates upwelling of the inflow into the photic zone. For a reservoir with no outflow, such as a reservoir that is filling, inflow that plunges below the photic zone remains at depth unless either entrainment or a bathymetric effect generates flow into the photic zone; nutrients are then released when the reservoir is drawn down, often in winter.

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4

GIANNETTO, Claudia, Stefania CASELLA, Giovanni CAOLA, and Giuseppe PICCIONE. "Photic and non-photic entrainment on daily rhythm of locomotor activity in goats." Animal Science Journal 81, no. 1 (February 2010): 122–28. http://dx.doi.org/10.1111/j.1740-0929.2009.00707.x.

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5

Glass, J. David, Suzette D. Tardif, Robert Clements, and N. Mrosovsky. "Photic and nonphotic circadian phase resetting in a diurnal primate, the common marmoset." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 280, no. 1 (January 1, 2001): R191—R197. http://dx.doi.org/10.1152/ajpregu.2001.280.1.r191.

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Despite the considerable literature on circadian entrainment, there is little information on this subject in diurnal mammals. Contributing to this lack of understanding is the problem of separating photic from nonphotic (behavioral) phase-resetting events in diurnal species. In the present study, photic phase resetting was obtained in diurnal common marmosets held under constant dim light (DimDim; <0.5 lx) by using a 20-s pulse of bright light to minimize time available for behavioral arousal. This stimulus elicited phase advances at circadian time (CT) 18–22 and phase delays at CT9–12. Daily presentation of these 20-s pulses produced entrainment with a phase angle of ∼11 h (0 h = activity onset). Nonphotic phase resetting was obtained under DimDim with the use of a 1-h-induced activity pulse, consisting of intermittent cage agitation and water sprinkling, delivered in total darkness to minimize photic effects. This stimulus caused phase delays at CT20–24, and entrainment to a scheduled daily regimen of these pulses occurred with a phase angle of ∼0 h. These results indicate that photic and nonphotic phase-response curves (PRCs) of marmosets are similar to those of nocturnal rodents and that nonphotic PRCs are keyed to the phase of the suprachiasmatic nucleus pacemaker, not to the phase of the activity-rest cycle.

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6

Dallmann, Robert, Jason P. DeBruyne, and David R. Weaver. "Photic Resetting and Entrainment in CLOCK-Deficient Mice." Journal of Biological Rhythms 26, no. 5 (September 15, 2011): 390–401. http://dx.doi.org/10.1177/0748730411414345.

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7

Ruby, Christina L., Natalie M. Verbanes, Kaitlyn N. Palmer, Catherine F. Zisk, David J. Bunion, and Laura N. Marinos. "Caffeine Delays Light-entrained Activity and Potentiates Circadian Photic Phase-resetting in Mice." Journal of Biological Rhythms 33, no. 5 (July 23, 2018): 523–34. http://dx.doi.org/10.1177/0748730418789236.

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Caffeine is widely used to reduce sedation and increase alertness. However, long-term caffeine use may disrupt circadian (daily, 24-h) rhythms and thereby negatively affect health. Here, we examined the effect of caffeine on photic regulation of circadian activity rhythms in mice. We found that entrainment to a standard 12-h light, 12-h dark (LD) photocycle was delayed during oral self-administration of caffeine. Both acute, high-dose caffeine and chronic, oral caffeine exposure potentiated photic phase-delays in mice, suggesting a possible mechanism by which entrainment to LD was delayed. The effect of caffeine on photic phase-resetting was mimicked by administration of adenosine A1, but not A2A, receptor antagonist in mice. Our results support the hypothesis that caffeine interferes with the ability of the circadian clock to respond normally to light.

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8

Rea, Michael A., and Gary G. E. Pickard. "Serotonergic Modulation of Photic Entrainment in the Syrian Hamster." Biological Rhythm Research 31, no. 3 (July 2000): 284–314. http://dx.doi.org/10.1076/0929-1016(200007)31:3;1-k;ft284.

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9

Boulos, Ziad, M. Mila Macchi, and Michael Terman. "Twilights Widen the Range of Photic Entrainment in Hamsters." Journal of Biological Rhythms 17, no. 4 (August 2002): 353–63. http://dx.doi.org/10.1177/074873002129002654.

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10

Illnerová, Helena, and Alena Sumová. "Photic Entrainment of the Mammalian Rhythm in Melatonin Production." Journal of Biological Rhythms 12, no. 6 (December 1997): 547–55. http://dx.doi.org/10.1177/074873049701200609.

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11

Ruby, Christina L., Allison J. Brager, Marc A. DePaul, Rebecca A. Prosser, and J. David Glass. "Chronic ethanol attenuates circadian photic phase resetting and alters nocturnal activity patterns in the hamster." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 297, no. 3 (September 2009): R729—R737. http://dx.doi.org/10.1152/ajpregu.00268.2009.

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Acute ethanol (EtOH) administration impairs circadian clock phase resetting, suggesting a mode for the disruptive effect of alcohol abuse on human circadian rhythms. Here, we extend this research by characterizing the chronobiological effects of chronic alcohol consumption. First, daily profiles of EtOH were measured in the suprachiasmatic nucleus (SCN) and subcutaneously using microdialysis in hamsters drinking EtOH. In both cases, EtOH peaked near lights-off and declined throughout the dark-phase to low day-time levels. Drinking bouts preceded EtOH peaks by ∼20 min. Second, hamsters chronically drinking EtOH received a light pulse during the late dark phase [Zeitgeber time (ZT) 18.5] to induce photic phase advances. Water controls had shifts of 1.2 ± 0.2 h, whereas those drinking 10% and 20% EtOH had much reduced shifts (0.5 ± 0.1 and 0.3 ± 0.1 h, respectively; P < 0.001 vs. controls). Third, incremental decreases in light intensity (270 lux to 0.5 lux) were used to explore chronic EtOH effects on photic entrainment and rhythm stability. Activity onset was unaffected by 20% EtOH at all light intensities. Conversely, the 24-h pattern of activity bouts was disrupted by EtOH under all light intensities. Finally, replacement of chronic EtOH with water was used to examine withdrawal effects. Water controls had photic phase advances of 1.1 ± 0.3 h, while hamsters deprived of EtOH for 2–3 days showed enhanced shifts (2.1 ± 0.3 h; P < 0.05 vs. controls). Thus, in chronically drinking hamsters, brain EtOH levels are sufficient to inhibit photic phase resetting and disrupt circadian activity. Chronic EtOH did not impair photic entrainment; however, its replacement with water potentiated photic phase resetting.

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12

Kas, Martien J. H., and Dale M. Edgar. "Photic phase response curve in Octodon degus: assessment as a function of activity phase preference." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, no. 5 (May 1, 2000): R1385—R1389. http://dx.doi.org/10.1152/ajpregu.2000.278.5.r1385.

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Light exposure during the early and late subjective night generally phase delays and advances circadian rhythms, respectively. However, this generality was recently questioned in a photic entrainment study in Octodon degus. Because degus can invert their activity phase preference from diurnal to nocturnal as a function of activity level, assessment of phase preference is critical for computations of phase reference [circadian time (CT) 0] toward the development of a photic phase response curve. After determining activity phase preference in a 24-h light-dark cycle (LD 12:12), degus were released in constant darkness. In this study, diurnal ( n = 5) and nocturnal ( n = 7) degus were randomly subjected to 1-h light pulses (30–35 lx) at many circadian phases (CT 1–6: n= 7; CT 7–12: n = 8; CT 13–18: n = 8; and CT 19–24: n = 7). The circadian phase of body temperature (Tb) onset was defined as CT 12 in nocturnal animals. In diurnal animals, CT 0 was determined as Tb onset + 1 h. Light phase delayed and advanced circadian rhythms when delivered during the early (CT 13–16) and late (CT 20–23) subjective night, respectively. No significant phase shifts were observed during the middle of the subjective day (CT 3–10). Thus, regardless of activity phase preference, photic entrainment of the circadian pacemaker in Octodon degus is similar to most other diurnal and nocturnal species, suggesting that entrainment mechanisms do not determine overt diurnal and nocturnal behavior.

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13

Castillo, Marina R., Kelly J. Hochstetler, Ronald J. Tavernier, Dana M. Greene, and Abel Bult-Ito. "Entrainment of the master circadian clock by scheduled feeding." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 287, no. 3 (September 2004): R551—R555. http://dx.doi.org/10.1152/ajpregu.00247.2004.

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The master circadian clock, located in the mammalian suprachiasmatic nuclei (SCN), generates and coordinates circadian rhythmicity, i.e., internal organization of physiological and behavioral rhythms that cycle with a near 24-h period. Light is the most powerful synchronizer of the SCN. Although other nonphotic cues also have the potential to influence the circadian clock, their effects can be masked by photic cues. The purpose of this study was to investigate the ability of scheduled feeding to entrain the SCN in the absence of photic cues in four lines of house mouse ( Mus domesticus). Mice were initially housed in 12:12-h light/dark cycle with ad libitum access to food for 6 h during the light period followed by 4–6 mo of constant dark under the same feeding schedule. Wheel running behavior suggested and circadian PER2 protein expression profiles in the SCN confirmed entrainment of the master circadian clock to the onset of food availability in 100% (49/49) of the line 2 mice in contrast to only 4% (1/24) in line 3 mice. Mice from line 1 and line 4 showed intermediate levels of entrainment, 57% (8/14) and 39% (7/18), respectively. The predictability of entrainment vs. nonentrainment in line 2 and line 3 and the novel entrainment process provide a powerful tool with which to further elucidate mechanisms involved in entrainment of the SCN by scheduled feeding.

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14

Nelson, Dwight E., and Joseph S. Takahashi. "Integration and saturation within the circadian photic entrainment pathway of hamsters." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 277, no. 5 (November 1, 1999): R1351—R1361. http://dx.doi.org/10.1152/ajpregu.1999.277.5.r1351.

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The sensitivity of the visual pathway that subserves circadian entrainment was measured in hamsters after prior stimulation and using trains of multiple pulses. Immediately after subsaturating stimulation in the late subjective night, there was a significant decrease in responsiveness that persisted for at least 1 h. The reduced responsiveness was not due to light adaptation (shifting of the stimulus-response curve) but rather to response saturation, which appeared to reduce the sensitivity to subsequent stimulation and limit the maximum response of the pacemaker. The system, therefore, integrates the total number of photons delivered in two light stimuli separated in time by up to 1 h. The responsiveness was also measured using stimulus trains containing 10–1,000 individual pulses of equal irradiance and equal total photons. Results suggest that this pathway is responsive to the total photons delivered in all of the stimuli and is not responsive to light onsets or offsets associated with individual stimuli. These data outline several fundamental characteristics of phase shifting for the circadian photic entrainment pathway in hamsters. Knowledge of these characteristics is important for designing and interpreting results of future studies to dissect the cellular and molecular nature of the mammalian circadian clock and for understanding how visual information affects the cellular clock during entrainment.

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15

Khammanivong, Ali, and Dwight E. Nelson. "Light Pulses Suppress Responsiveness within the Mouse Photic Entrainment Pathway." Journal of Biological Rhythms 15, no. 5 (October 2000): 393–405. http://dx.doi.org/10.1177/074873040001500505.

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16

Sollars, Patricia J., Malcolm D. Ogilvie, Anne M. Simpson, and Gary E. Pickard. "Photic Entrainment Is Altered in the 5-HT1BReceptor Knockout Mouse." Journal of Biological Rhythms 21, no. 1 (February 2006): 21–32. http://dx.doi.org/10.1177/0748730405283765.

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17

Zordan, Mauro A., Ezio Rosato, Alberto Piccin, and Russell Foster. "Photic entrainment of the circadian clock: from Drosophila to mammals." Seminars in Cell & Developmental Biology 12, no. 4 (August 2001): 317–28. http://dx.doi.org/10.1006/scdb.2001.0259.

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18

Dixit, Anand S., Namram S. Singh, and Iadalangki Bamon. "Photoperiodic time measurement and photoentrainment of a circadian locomotor activity rhythm in subtropical tree sparrows." Photochemical & Photobiological Sciences 16, no. 7 (2017): 1146–52. http://dx.doi.org/10.1039/c6pp00271d.

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Experiments were performed on the subtropical tree sparrow (Passer montanus) to investigate the involvement of an endogenous circadian rhythm in photoperiodic time measurement during the initiation of gonadal growth and functions and also to study the photic entrainment of the circadian activity rhythm.

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19

Butler, Matthew P., and Rae Silver. "Divergent photic thresholds in the non-image-forming visual system: entrainment, masking and pupillary light reflex." Proceedings of the Royal Society B: Biological Sciences 278, no. 1706 (September 22, 2010): 745–50. http://dx.doi.org/10.1098/rspb.2010.1509.

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Light is the principal cue that entrains the circadian timing system, but the threshold of entrainment and the relative contributions of the retinal photoreceptors—rods, cones and intrinsically photosensitive retinal ganglion cells—are not known. We measured thresholds of entrainment of wheel-running rhythms at three wavelengths, and compared these to thresholds of two other non-image-forming visual system functions: masking and the pupillary light reflex (PLR). At the entrainment threshold, the relative spectral sensitivity and absolute photon flux suggest that this threshold is determined by rods. Dim light that entrained mice failed to elicit either masking or PLR; in general, circadian entrainment is more sensitive by 1–2 log units than other measures of the non-image-forming visual system. Importantly, the results indicate that dim light can entrain circadian rhythms even when it fails to produce more easily measurable acute responses to light such as phase shifting and melatonin suppression. Photosensitivity to one response, therefore, cannot be generalized to other non-image-forming functions. These results also impact practical problems in selecting appropriate lighting in laboratory animal husbandry.

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20

Challet, Etienne. "Minireview: Entrainment of the Suprachiasmatic Clockwork in Diurnal and Nocturnal Mammals." Endocrinology 148, no. 12 (December 1, 2007): 5648–55. http://dx.doi.org/10.1210/en.2007-0804.

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Daily rhythmicity, including timing of wakefulness and hormone secretion, is mainly controlled by a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN clockwork involves various clock genes, with specific temporal patterns of expression that are similar in nocturnal and diurnal species (e.g. the clock gene Per1 in the SCN peaks at midday in both categories). Timing of sensitivity to light is roughly similar, during nighttime, in diurnal and nocturnal species. Molecular mechanisms of photic resetting are also comparable in both species categories. By contrast, in animals housed in constant light, exposure to darkness can reset the SCN clock, mostly during the resting period, i.e. at opposite circadian times between diurnal and nocturnal species. Nonphotic stimuli, such as scheduled voluntary exercise, food shortage, exogenous melatonin, or serotonergic receptor activation, are also capable of shifting the master clock and/or modulating photic synchronization. Comparison between day- and night-active species allows classifications of nonphotic cues in two, arousal-independent and arousal-dependent, families of factors. Arousal-independent factors, such as melatonin (always secreted during nighttime, independently of daily activity pattern) or γ-aminobutyric acid (GABA), have shifting effects at the same circadian times in both nocturnal and diurnal rodents. By contrast, arousal-dependent factors, such as serotonin (its cerebral levels follow activity pattern), induce phase shifts only during resting and have opposite modulating effects on photic resetting between diurnal and nocturnal species. Contrary to light and arousal-independent nonphotic cues, arousal-dependent nonphotic stimuli provide synchronizing feedback signals to the SCN clock in circadian antiphase between nocturnal and diurnal animals.

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21

Golombek, Diego A., and Ruth E. Rosenstein. "Physiology of Circadian Entrainment." Physiological Reviews 90, no. 3 (July 2010): 1063–102. http://dx.doi.org/10.1152/physrev.00009.2009.

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Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of ∼24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber (“time giver”) signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments.

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22

Erkert, Hans G., Viola Gburek, and Angelika Scheideler. "Photic entrainment and masking of prosimian circadian rhythms (Otolemur garnettii, Primates)." Physiology & Behavior 88, no. 1-2 (June 2006): 39–46. http://dx.doi.org/10.1016/j.physbeh.2006.03.003.

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23

Schöttner, Konrad, Jane Hauer, and Dietmar Weinert. "Non-parametric photic entrainment of Djungarian hamsters with different rhythmic phenotypes." Chronobiology International 33, no. 5 (March 31, 2016): 506–19. http://dx.doi.org/10.3109/07420528.2016.1160100.

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24

Lee, Theresa M., and Irving Zucker. "Suprachiasmatic Nucleus and Photic Entrainment of Circannual Rhythms in Ground Squirrels." Journal of Biological Rhythms 6, no. 4 (December 1991): 315–30. http://dx.doi.org/10.1177/074873049100600403.

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25

Ruis, J. F., W. J. Rietveld, and J. P. Buys. "Properties of parametric photic entrainment of circadian rhythms in the rat." Physiology & Behavior 50, no. 6 (December 1991): 1233–39. http://dx.doi.org/10.1016/0031-9384(91)90588-f.

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26

Rosenwasser, A. M., M. W. Pellowski, and E. D. Hendley. "Circadian timekeeping in hyperactive and hypertensive inbred rat strains." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 271, no. 3 (September 1, 1996): R787—R796. http://dx.doi.org/10.1152/ajpregu.1996.271.3.r787.

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Inbred strains have been used to study genetic and physiological relationships among different aspects of circadian timekeeping, as well as relationships between circadian rhythmicity and other strain-specific traits. The present study characterized several features of circadian timekeeping in genetically hyperactive (WKHA) and genetically hypertensive (WKHT) inbred strains, derived from spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. WKHAs and WKHTs differed in free-running period, steady-state entrainment to light-dark cycles, and photic phase shifting, and relationships among these measures were consistent with previous studies of species, strain, and individual differences. Because both WKHTs and SHRs show short circadian periods relative to their respective comparison strains, this trait may cosegregate genetically with hypertension. In contrast, because WKHAs and SHRs show similar photic entrainment and phase shifting, these circadian functions may cosegregate with open-field hyperactivity. Finally, because neither WKHAs nor WKHTs show the SHR's excessive levels of home-cage running wheel activity, this trait is not related to either hypertension or open-field activity. Further work would be required to elucidate specific genetic and/or physiological linkages among these variables.

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27

Moriya, Takahiro, Hironori Miyamura, Kazumasa Horikawa, and Shigenobu Shibata. "Glutamate receptor-mediated photic expression of Period genes in the hamster SCN and photic entrainment of the biological clock." Japanese Journal of Pharmacology 82 (2000): 109. http://dx.doi.org/10.1016/s0021-5198(19)47905-5.

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28

Cohen, Rotem, and Noga Kronfeld-Schor. "Individual variability and photic entrainment of circadian rhythms in golden spiny mice." Physiology & Behavior 87, no. 3 (March 2006): 563–74. http://dx.doi.org/10.1016/j.physbeh.2005.12.010.

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29

Moriya, Takahiro, Reiko Hara, Masayuki Ikeda, Koji Teshima, Masakazu Horikawa, Tohru Yoshioka, Charles N. Allen, and Shigenobu Shibata. "Potentiating effect of aniracetam on photic entrainment of circadian clock in rodents." Japanese Journal of Pharmacology 79 (1999): 113. http://dx.doi.org/10.1016/s0021-5198(19)34477-4.

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30

Holmes, M. M., and R. E. Mistlberger. "Food anticipatory activity and photic entrainment in food-restricted BALB/c mice." Physiology & Behavior 68, no. 5 (March 2000): 655–66. http://dx.doi.org/10.1016/s0031-9384(99)00231-0.

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31

Gerkema, M. P., J. J. Videler, J. de Wiljes, H. van Lavieren, H. Gerritsen, and M. Karel. "PHOTIC ENTRAINMENT OF CIRCADIAN ACTIVITY PATTERNS IN THE TROPICAL LABRID FISHHALICHOERES CHRYSUS." Chronobiology International 17, no. 5 (January 2000): 613–22. http://dx.doi.org/10.1081/cbi-100101068.

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32

Boulos, Z., M. Macchi, T. A. Houpt, and M. Terman. "Photic Entrainment in Hamsters: Effects of Simulated Twilights and Nest Box Availability." Journal of Biological Rhythms 11, no. 3 (September 1996): 216–33. http://dx.doi.org/10.1177/074873049601100304.

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33

Wee, Raymond, Ana Maria Castrucci, Ignacio Provencio, Lin Gan, and Russell N. Van Gelder. "Loss of Photic Entrainment and Altered Free-Running Circadian Rhythms inmath5−/−Mice." Journal of Neuroscience 22, no. 23 (December 1, 2002): 10427–33. http://dx.doi.org/10.1523/jneurosci.22-23-10427.2002.

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34

HASHIMOTO, Satoko, Kouji NAKAMURA, Sato HONMA, and Ken-ichi HONMA. "Non-photic entrainment of human rest-activity cycle independent of circadian pacemaker." Sleep and Biological Rhythms 2, no. 1 (February 2004): 29–36. http://dx.doi.org/10.1111/j.1479-8425.2003.00078.x.

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35

Miyasako, Yoko, and Kenji Tomioka. "Neuronal mechanisms for photic and thermoperiodic entrainment of Drosophila circadian locomotor rhythms." Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 145, no. 3-4 (November 2006): 415. http://dx.doi.org/10.1016/j.cbpb.2006.10.050.

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36

Glass, J. David, Allison J. Brager, Adam C. Stowie, and Rebecca A. Prosser. "Cocaine modulates pathways for photic and nonphotic entrainment of the mammalian SCN circadian clock." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 302, no. 6 (March 15, 2012): R740—R750. http://dx.doi.org/10.1152/ajpregu.00602.2011.

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Cocaine abuse is highly disruptive to circadian physiological and behavioral rhythms. The present study was undertaken to determine whether such effects are manifest through actions on critical photic and nonphotic regulatory pathways in the master circadian clock of the mouse suprachiasmatic nucleus (SCN). Impairment of SCN photic signaling by systemic (intraperitoneal) cocaine injection was evidenced by strong (60%) attenuation of light-induced phase-delay shifts of circadian locomotor activity during the early night. A nonphotic action of cocaine was apparent from its induction of 1-h circadian phase-advance shifts at midday. The serotonin receptor antagonist, metergoline, blocked shifting by 80%, implicating a serotonergic mechanism. Reverse microdialysis perfusion of the SCN with cocaine at midday induced 3.7 h phase-advance shifts. Control perfusions with lidocaine and artificial cerebrospinal fluid had little shifting effect. In complementary in vitro experiments, photic-like phase-delay shifts of the SCN circadian neuronal activity rhythm induced by glutamate application to the SCN were completely blocked by cocaine. Cocaine treatment of SCN slices alone at subjective midday, but not the subjective night, induced 3-h phase-advance shifts. Lidocaine had no shifting effect. Cocaine-induced phase shifts were completely blocked by metergoline, but not by the dopamine receptor antagonist, fluphenazine. Finally, pretreatment of SCN slices for 2 h with a low concentration of serotonin agonist (to block subsequent serotonergic phase resetting) abolished cocaine-induced phase shifts at subjective midday. These results reveal multiple effects of cocaine on adult circadian clock regulation that are registered within the SCN and involve enhanced serotonergic transmission.

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37

Ware, Jasmine V., O. Lynne Nelson, Charles T. Robbins, and Heiko T. Jansen. "Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 303, no. 9 (November 1, 2012): R890—R902. http://dx.doi.org/10.1152/ajpregu.00313.2012.

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Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in daylength (photoperiod). Ecological and evolutionary pressures have resulted in physiological specializations enabling animals to occupy a particular temporal niche within the diel cycle leading to characteristic activity patterns. In this study, we characterized the annual locomotor activity of captive brown bears (Ursus arctos). Locomotor activity was observed in 18 bears of varying ages and sexes during the active (Mar-Oct) and hibernating (Nov-Feb) seasons. All bears exhibited either crepuscular or diurnal activity patterns. Estimates of activity duration (α) and synchronization to the daily light:dark cycle (phase angles) indirectly measured photoresponsiveness. α increased as daylength increased but diverged near the autumnal equinox. Phase angles varied widely between active and hibernating seasons and exhibited a clear annual rhythm. To directly test the role of photoperiod, bears were exposed to controlled photoperiod alterations. Bears failed to alter their daily activity patterns (entrain) to experimental photoperiods during the active season. In contrast, photic entrainment was evident during hibernation when the daily photocycle was shifted and when bears were exposed to a skeleton (11:1:11:1) photoperiod. To test whether entrainment to nonphotic cues superseded photic entrainment during the active season, bears were exposed to a reversed feeding regimen (dark-fed) under a natural photocycle. Activity shifted entirely to a nocturnal pattern. Thus daily activity in brown bears is highly modifiable by photoperiod and food availability in a stereotypic seasonal fashion.

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Van Den Pol, Anthony N., Vinh Cao, and H. Craig Heller. "Circadian system of mice integrates brief light stimuli." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 275, no. 2 (August 1, 1998): R654—R657. http://dx.doi.org/10.1152/ajpregu.1998.275.2.r654.

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Light is the primary sensory stimulus that synchronizes or entrains the internal circadian rhythms of animals to the solar day. In mammals photic entrainment of the circadian pacemaker residing in the suprachiasmatic nuclei is due to the fact that light at certain times of day can phase shift the pacemaker. In this study we show that the circadian system of mice can integrate extremely brief, repeated photic stimuli to produce large phase shifts. A train of 2-ms light pulses delivered as one pulse every 5 or 60 s, with a total light duration of 120 ms, can cause phase shifts of several hours that endure for weeks. Single 2-ms pulses of light were ineffective. Thus these data reveal a property of the mammalian circadian clock: it can integrate and store latent sensory information in such a way that a series of extremely brief photic stimuli, each too small to cause a phase shift individually, together can cause a large and long-lasting change in behavior.

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Mohawk, Jennifer A., Katherine Cashen, and Theresa M. Lee. "Inhibiting cortisol response accelerates recovery from a photic phase shift." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 288, no. 1 (January 2005): R221—R228. http://dx.doi.org/10.1152/ajpregu.00272.2004.

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Jetlag results when a temporary loss of circadian entrainment alters phase relationships among internal rhythms and between an organism and the outside world. After a large shift in the light-dark (LD) cycle, rapid recovery of entrainment minimizes the negative effects of internal circadian disorganization. There is evidence in the existing literature for an activation of the hypothalamic-pituitary-adrenal (HPA) axis after a photic phase shift, and it is possible that the degree of HPA-axis response is a determining factor of reentrainment time. This study utilized a diurnal rodent, Octodon degus, to test the prediction that the alteration of cortisol levels would affect the reentrainment rate of circadian locomotor rhythms. In experiment 1, we examined the effects of decreased cortisol (using metyrapone, an 11β-hydroxylase inhibitor) on the rate of running-wheel rhythm recovery after a 6-h photic phase advance. Metyrapone treatment significantly shortened the length of time it took animals to entrain to the new LD cycle (11.5% acceleration). In experiment 2, we examined the effects of increased cortisol on the rate of reentrainment after a 6-h photic phase advance. Increasing plasma cortisol levels increased the number of days (8%) animals took to reentrain running-wheel activity rhythms, but this effect did not reach significance. A third experiment replicated the results of experiment 1 and also demonstrated that suppression of HPA activity via dexamethasone injection is capable of accelerating reentrainment rates by ∼33%. These studies provide support for an interaction between the stress axis and circadian rhythms in determining the rate of recovery from a phase shift of the LD cycle.

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Ruby, Norman F., Tom Kang, and H. Craig Heller. "Melatonin attenuates photic disruption of circadian rhythms in Siberian hamsters." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, no. 4 (October 1, 1997): R1540—R1549. http://dx.doi.org/10.1152/ajpregu.1997.273.4.r1540.

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Body temperature (Tb) was recorded via a biotelemetry system from 28 adult male Siberian hamsters maintained in a light-dark (LD) cycle of 16 h light/day for several months. After Tb was recorded for 3 wk, the LD cycle was phase delayed by extending the light phase by 5 h for 1 day; animals remained on a 16:8 LD cycle for the remainder of the experiment. Hamsters were injected daily with melatonin or vehicle solution for several weeks, beginning either 2 mo after ( experiment 1) or on the day of ( experiment 2) the phase shift; injections occurred within 30 min of dark onset. In experiment 1, 75% of animals free ran with circadian periods >24 h, beginning on the day of the phase shift, and never reentrained to the LD cycle; no hamsters unambiguously entrained to daily injections. In contrast, 78% of animals in experiment 2 entrained to melatonin injections, and 71% of those animals subsequently reentrained to the photocycle when the injection regimen ended. No vehicle-treated animals entrained to the injection schedule. Melatonin had no effect on daily mean Tb and Tb rhythm amplitude in either experiment; however, melatonin doubled the duration of a hyperthermic response that occurred after each injection. Thus melatonin can prevent loss of entrainment induced by a phase shift of the LD cycle but cannot restore entrainment to free-running animals. Failure to reentrain in the presence of two appropriately coordinated entraining agents also suggests that a phase shift of the photocycle can diminish the sensitivity of the circadian system to both photic and nonphotic input.

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Wiater, Michael F., Ai-Jun Li, Thu T. Dinh, Heiko T. Jansen, and Sue Ritter. "Leptin-sensitive neurons in the arcuate nucleus integrate activity and temperature circadian rhythms and anticipatory responses to food restriction." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, no. 8 (October 15, 2013): R949—R960. http://dx.doi.org/10.1152/ajpregu.00032.2013.

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Previously, we investigated the role of neuropeptide Y and leptin-sensitive networks in the mediobasal hypothalamus in sleep and feeding and found profound homeostatic and circadian deficits with an intact suprachiasmatic nucleus. We propose that the arcuate nuclei (Arc) are required for the integration of homeostatic circadian systems, including temperature and activity. We tested this hypothesis using saporin toxin conjugated to leptin (Lep-SAP) injected into Arc in rats. Lep-SAP rats became obese and hyperphagic and progressed through a dynamic phase to a static phase of growth. Circadian rhythms were examined over 49 days during the static phase. Rats were maintained on a 12:12-h light-dark (LD) schedule for 13 days and, thereafter, maintained in continuous dark (DD). After the first 13 days of DD, food was restricted to 4 h/day for 10 days. We found that the activity of Lep-SAP rats was arrhythmic in DD, but that food anticipatory activity was, nevertheless, entrainable to the restricted feeding schedule, and the entrained rhythm persisted during the subsequent 3-day fast in DD. Thus, for activity, the circuitry for the light-entrainable oscillator, but not for the food-entrainable oscillator, was disabled by the Arc lesion. In contrast, temperature remained rhythmic in DD in the Lep-SAP rats and did not entrain to restricted feeding. We conclude that the leptin-sensitive network that includes the Arc is required for entrainment of activity by photic cues and entrainment of temperature by food, but is not required for entrainment of activity by food or temperature by photic cues.

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Sun, Jonathan, Deborah A. M. Joye, Andrew H. Farkas, and Michael R. Gorman. "Photoperiodic Requirements for Induction and Maintenance of Rhythm Bifurcation and Extraordinary Entrainment in Male Mice." Clocks & Sleep 1, no. 3 (July 4, 2019): 290–305. http://dx.doi.org/10.3390/clockssleep1030025.

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Exposure of mice to a 24 h light:dark:light:dark (LDLD) cycle with dimly illuminated nights induces the circadian timing system to program two intervals of activity and two intervals of rest per 24 h cycle and subsequently allows entrainment to a variety of extraordinary light regimens including 30 h LDLD cycles. Little is known about critical lighting requirements to induce and maintain this non-standard entrainment pattern, termed “bifurcation,” and to enhance the range of apparent entrainment. The current study determined the necessary duration of the photophase for animals to bifurcate and assessed whether requirements for maintenance differed from those for induction. An objective index of bifurcated entrainment varied with length of the photophase over 4–10 h durations, with highest values at 8 h. To assess photic requirements for the maintenance of bifurcation, mice from each group were subsequently exposed to the LDLD cycle with 4 h photophases. While insufficient to induce bifurcation, this photoperiod maintained bifurcation in mice transferred from inductive LDLD cycles. Entrainment to 30 h LDLD cycles also varied with photoperiod duration. These studies characterize non-invasive tools that reveal latent flexibility in the circadian control of rest/activity cycles with important translational potential for addressing needs of human shift-workers.

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Beaulé, Christian, and Shimon Amir. "Photic entrainment and induction of immediate-early genes within the rat circadian system." Brain Research 821, no. 1 (March 1999): 95–100. http://dx.doi.org/10.1016/s0006-8993(99)01073-2.

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Schmidt, S., M. Scholz, L. Haberbosch, A. Mante, K. Obermayer, and S. A. Brandt. "P273: Fast induction of alpha entrainment with bandwidth confined electric and photic stimulation." Clinical Neurophysiology 125 (June 2014): S122. http://dx.doi.org/10.1016/s1388-2457(14)50394-x.

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Pasqualetti, Massimo, Cristiano Bertolucci, Michela Ori, Augusto Innocenti, Maria C. Magnone, Willem J. De Grip, Irma Nardi, and Augusto Foa. "Identification of circadian brain photoreceptors mediating photic entrainment of behavioural rhythms in lizards." European Journal of Neuroscience 18, no. 2 (July 2003): 364–72. http://dx.doi.org/10.1046/j.1460-9568.2003.02770.x.

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Cao, R., A. Li, H. y. Cho, B. Lee, and K. Obrietan. "Mammalian Target of Rapamycin Signaling Modulates Photic Entrainment of the Suprachiasmatic Circadian Clock." Journal of Neuroscience 30, no. 18 (May 5, 2010): 6302–14. http://dx.doi.org/10.1523/jneurosci.5482-09.2010.

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Duffield, Giles E., Nathan P. Watson, Akio Mantani, Stuart N. Peirson, Maricela Robles-Murguia, Jennifer J. Loros, Mark A. Israel, and Jay C. Dunlap. "A Role for Id2 in Regulating Photic Entrainment of the Mammalian Circadian System." Current Biology 19, no. 4 (February 2009): 297–304. http://dx.doi.org/10.1016/j.cub.2008.12.052.

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Sage, Dominique, Julien Ganem, Fabienne Guillaumond, Geneviève Laforge-Anglade, Anne-Marie François-Bellan, Olivier Bosler, and Denis Becquet. "Influence of the Corticosterone Rhythm on Photic Entrainment of Locomotor Activity in Rats." Journal of Biological Rhythms 19, no. 2 (April 2004): 144–56. http://dx.doi.org/10.1177/0748730403261894.

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Boudard, Domitille L., Jorge Mendoza, and David Hicks. "Loss of photic entrainment at low illuminances in rats with acute photoreceptor degeneration." European Journal of Neuroscience 30, no. 8 (October 2009): 1527–36. http://dx.doi.org/10.1111/j.1460-9568.2009.06935.x.

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Vanlalnghaka, C., V. L. Keny, Moses K. Satralkar, M. S. Kasture, Rajneesh J. Barnabas, and Dilip S. Joshi. "Effect of aging on the photic entrainment in the frugivorous bat,Rousettus leschenaulti." Biological Rhythm Research 37, no. 3 (June 2006): 247–53. http://dx.doi.org/10.1080/09291010600577082.

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