Articoli di riviste: "Rats Physiology"

1

Barney, Christopher C. "Restrained rats and the observer effect in physiology". Experimental Physiology 96, n. 12 (23 novembre 2011): 1253–54. http://dx.doi.org/10.1113/expphysiol.2011.061267.

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Musch, T. I., A. Bruno, G. E. Bradford, A. Vayonis e R. L. Moore. "Measurements of metabolic rate in rats: a comparison of techniques". Journal of Applied Physiology 65, n. 2 (1 agosto 1988): 964–70. http://dx.doi.org/10.1152/jappl.1988.65.2.964.

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Two different open-circuit techniques of measuring metabolic rate were examined in rats at rest and during exercise. With one technique ambient air was drawn through a tightly fitting mask that was secured to the rat's head, whereas with the other technique the rat was placed into and ambient air was drawn through a Plexiglas box. Two series of experiments were performed. In series I, two groups were studied that consisted of rats that had received myocardial infarctions produced by coronary arterial ligations and rats that had received sham operations. In this series of experiments O2 uptake (VO2) and CO2 production (VCO2) were measured at rest, during four levels of submaximal exercise, and during maximal treadmill exercise in the same group of rats by use of both techniques in random order. VO2, VCO2, and the calculated respiratory exchange ratio (R) were similar at rest, during the highest level of submaximal exercise (20% grade, 37 m/min), and during maximal exercise; however, VO2 and VCO2 were significantly lower with the metabolic box technique compared with the mask technique during the three lowest work loads (5% grade, 19 m/min; 10% grade, 24 m/min; and 15% grade, 31 m/min). These differences appeared to be associated with a change in gait produced when the mask was worn. In series II, the arterial blood gas and acid-base responses to both submaximal and maximal exercise were measured using both techniques in a group of instrumented rats that had a catheter placed into the right carotid artery.(ABSTRACT TRUNCATED AT 250 WORDS)

3

Guerrero, Fr, e H. Burnet. "Effects of compression rate on rats carotid blood flow". Archives of Physiology and Biochemistry 103, n. 2 (gennaio 1995): 196–201. http://dx.doi.org/10.3109/13813459508996133.

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Sokoloff, Greta, Robert F. Kirby e Mark S. Blumberg. "Further evidence that BAT thermogenesis modulates cardiac rate in infant rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 274, n. 6 (1 giugno 1998): R1712—R1717. http://dx.doi.org/10.1152/ajpregu.1998.274.6.r1712.

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Previous research in infant rats suggested that brown adipose tissue (BAT), by providing warm blood to the heart during moderate cold exposure, protects cardiac rate. This protective role for BAT thermogenesis was examined further in the present study. In experiment 1, 1-wk-old rats in a warm environment were pretreated with saline or chlorisondamine (a ganglionic blocker), and then BAT thermogenesis was stimulated by injection with the β3-agonist CL-316243. In experiment 2, pups were pretreated with chlorisondamine and injected with CL-316243, and after BAT thermogenesis was stimulated the interscapular region of the pups was cooled externally with a thermode. In both experiments, cardiac rate, oxygen consumption, and physiological temperatures were monitored. Activation of BAT thermogenesis substantially increased cardiac rate in saline- and chlorisondamine-treated pups, and focal cooling of the interscapular region was sufficient to lower cardiac rate. The results of these studies support the hypothesis that BAT thermogenesis contributes directly to the modulation of cardiac rate.

5

Holloszy, John O. "Mortality rate and longevity of food-restricted exercising male rats: a reevaluation". Journal of Applied Physiology 82, n. 2 (1 febbraio 1997): 399–403. http://dx.doi.org/10.1152/jappl.1997.82.2.399.

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Holloszy, John O. Mortality rate and longevity of food-restricted exercising male rats: a reevaluation. J. Appl. Physiol. 82(2): 399–403, 1997.—Food restriction increases the maximal longevity of rats. Male rats do not increase their food intake to compensate for the increase in energy expenditure in response to exercise. However, a decrease in the availability of energy for growth and cell proliferation that induces an increase in maximal longevity in sedentary rats only results in an improvement in average survival, with no extension of maximal life span, when caused by exercise. In a previous study (J. O. Holloszy and K. B. Schechtman. J. Appl. Physiol. 70: 1529–1535, 1991), to test the possibility that exercise prevents the extension of life span by food restriction, wheel running and food restriction were combined. The food-restricted runners showed the same increase in maximal life span as food-restricted sedentary rats but had an increased mortality rate during the first one-half of their mortality curve. The purpose of the present study was to determine the pathological cause of this increased early mortality. However, in contrast to our previous results, the food-restricted wheel-running rats in this study showed no increase in early mortality, and their survival curves were virtually identical to those of sedentary animals that were food restricted so as to keep their body weights the same as those of the runners. Thus it is possible that the rats in the previous study had a health problem that had no effect on longevity except when both food restriction and exercise were superimposed on it. Possibly of interest in this regard, the rats in this study did considerably more voluntary running than those in the previous study. It is concluded that 1) moderate caloric restriction combined with exercise does not normally increase the early mortality rate in male rats, 2) exercise does not interfere with the extension of maximal life span by food restriction, and 3) the beneficial effects of food restriction and exercise on survival are not additive or synergistic.

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Odenweller, C. M., C. T. Hsu, E. Sipe, J. P. Layshock, S. Varyani, R. L. Rosian e S. E. DiCarlo. "Laboratory exercise using "virtual rats" to teach endocrine physiology." Advances in Physiology Education 273, n. 6 (dicembre 1997): S24. http://dx.doi.org/10.1152/advances.1997.273.6.s24.

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Animal experimentation is limited in many curricula due to the expense, lack of adequate animal facilities and equipment, and limited experience of the teachers. There are also ethical concerns dealing with the comfort and safety of the animals. To overcome these obstacles, we developed a "dry laboratory" using "virtual rats." The "virtual rat" eliminates the obstacles inherent in animal experimentation, such as inadequate budgets, as well as avoiding important animal rights issues. Furthermore, no special materials are required for the completion of this exercise. Our goal in developing this dry laboratory was to create an experience that would provide students with an appreciation for the value of laboratory data collection and analysis. Students are exposed to the challenge of animal experimentation, experimental design, data collection, and analysis and interpretation without the issues surrounding the use of live animals.

7

Hofer, M. A. "Nutrient control of cardiac rate in infant rats: role of arterial baroreceptors". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 249, n. 4 (1 ottobre 1985): R443—R448. http://dx.doi.org/10.1152/ajpregu.1985.249.4.r443.

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A surgical procedure is described for the deafferentation of carotid sinus (CS) and aortic depressor (AD) baroreceptors in 2-wk suckling rats. Baroreflex testing in unanesthetized pups showed that cardiac rate responses to acute elevations of blood pressure were reduced to less than 9% of controls after combined denervation (CSAD), 28% after AD and 47% after CS denervation at 4 h. After 24 h of nutrient deprivation, resting cardiac rates of sham operated controls fell a mean of -148 beat/min, significantly more than CS, AD, or CSAD groups (P less than 0.01). Baroreflex test responses in individuals correlated significantly with their later responses to nutrient deprivation (r = 0.67, P less than 0.01). There were no significant differences in base-line cardiac rate, systolic blood pressure, or cardiac rate during 24 h intragastric milk infusion between deafferented and control pups. These experiments suggest that arterial baroreceptors are important in the cardiovascular adjustments after nutrient deprivation in suckling rats.

8

Holloszy, J. O., e E. K. Smith. "Longevity of cold-exposed rats: a reevaluation of the "rate-of-living theory"". Journal of Applied Physiology 61, n. 5 (1 novembre 1986): 1656–60. http://dx.doi.org/10.1152/jappl.1986.61.5.1656.

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It has been postulated that increased energy expenditure results in shortened survival. To test this “rate-of-living theory” we examined the effect of raising energy expenditure by means of cold exposure on the longevity of rats. Male 6-mo-old SPF Long-Evans rats were gradually accustomed to immersion in cool water (23 degrees C). After 3 mo they were standing in the cool water for 4 h/day, 5 days/wk. They were maintained on this program until age 32 mo. The cold exposure resulted in a 44% increase in food intake (P less than 0.001). Despite their greater food intake, the cold-exposed rats' body weights were significantly lower than those of control animals from age 11 to 32 mo. The average age at death of the cold-exposed rats was 968 +/- 141 days compared with 923 +/- 159 days for the controls. The cold exposure appeared to protect against neoplasia, particularly sarcomas; only 24% of the necropsied cold-exposed rats had malignancies compared with 57% for the controls. The results of this study provide no support for the concept that increased energy expenditure decreases longevity.

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Vitela, M., M. Herrera-Rosales, J. R. Haywood e S. W. Mifflin. "Baroreflex regulation of renal sympathetic nerve activity and heart rate in renal wrap hypertensive rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 288, n. 4 (aprile 2005): R856—R862. http://dx.doi.org/10.1152/ajpregu.00620.2004.

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Despite its usefulness as a nongenetic model of hypertension, little information is available regarding baroreflex function in the Grollman, renal wrap model of hypertension in the rat. Baroreflex regulation of renal sympathetic nerve activity (RSNA) and heart rate (HR) were studied in male, Sprague-Dawley rats hypertensive (HT) for 1 or 4–6 wk after unilateral nephrectomy and figure-8 ligature around the remaining kidney or normotensive (NT) after sham surgery. Rats were anesthetized with Inactin and RSNA, and HR was recorded during intravenous infusions of sodium nitroprusside or phenylephrine to lower or raise mean arterial pressure (MAP). Response curves were analyzed using a logistic sigmoid function. In 1- and 4-wk HT rats the midpoints of RSNA and HR reflex curves were shifted to the right ( P < 0.05). Comparing NT to 1- or 4-wk HT rats, the gain of RSNA-MAP curves was no different; however, gain was reduced in the HR-MAP curves at both 1 and 4 wk in HT rats ( P < 0.05). In anesthetized rats the HR range was small; therefore, MAP and HR were measured in conscious rats during intravenous injections of three doses of phenylephrine and three doses of sodium nitroprusside. Linear regressions revealed a reduced slope in both 1- and 4-wk HT rats compared with NT rats ( P < 0.05). The results indicate that baroreflex curves are shifted to the right, to higher pressures, in hypertension. After 1–4 wk of hypertension the gain of baroreflex regulation of RSNA is not altered; however, the gain of HR regulation is reduced.

10

Jaldow, Eli J., e David A. OAkley. "Performance on a differential reinforcement of low-rate schedule in neodecorticated rats and rats with hippocampal lesions". Psychobiology 18, n. 4 (dicembre 1990): 394–403. http://dx.doi.org/10.3758/bf03333086.

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Shen, Yiming, Jin Bong Park, So Yeong Lee, Seong Kyu Han e Pan Dong Ryu. "Exercise training normalizes elevated firing rate of hypothalamic presympathetic neurons in heart failure rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 316, n. 2 (1 febbraio 2019): R110—R120. http://dx.doi.org/10.1152/ajpregu.00225.2018.

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Exercise training (ExT) normalizes elevated sympathetic nerve activity in heart failure (HF), but the underlying mechanisms are not well understood. In this study, we examined the effects of 3 wk of ExT on the electrical activity of the hypothalamic presympathetic neurons in the brain slice of HF rats. HF rats were prepared by ligating the left descending coronary artery. The electrophysiological properties of paraventricular nucleus neurons projecting to the rostral ventrolateral medulla (PVN-RVLM) were examined using the slice patch-clamp technique. The neuronal firing rate was elevated in HF rats, and ExT induced a reduction in the firing rate ( P < 0.01). This ExT-induced decrease in the firing rate was associated with an increased frequency of spontaneous and miniature inhibitory postsynaptic current (IPSCs; P < 0.05). There was no significant change in excitatory postsynaptic current. Replacing Ca2+ with Mg2+ in the recording solution reduced the elevated IPSC frequency in HF rats with ExT ( P < 0.01) but not in those without ExT, indicating an increase in the probability of GABA release. In contrast, ExT did not restore the reduced GABAA receptor-mediated tonic inhibitory current in HF rats. A GABAA receptor blocker (bicuculline, 20 μM) increased the firing rate in HF rats with ExT ( P < 0.01) but not in those without ExT. Collectively, these results show that ExT normalized the elevated firing activity by increasing synaptic GABA release in PVN-RVLM neurons in HF rats. Our findings provide a brain mechanism underlying the beneficial effects of ExT in HF, which may shed light on the pathophysiology of other diseases accompanied by sympathetic hyperactivation.

12

Wang, Pei, Hui Du, Ruo-Yu Zhang, Yun-Feng Guan, Tian-Ying Xu, Quan-Yi Xu, Ding-Feng Su e Chao-Yu Miao. "Circulating and local visfatin/Nampt/PBEF levels in spontaneously hypertensive rats, stroke-prone spontaneously hypertensive rats and Wistar-Kyoto rats". Journal of Physiological Sciences 60, n. 5 (24 luglio 2010): 317–24. http://dx.doi.org/10.1007/s12576-010-0103-1.

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El-Mas, Mahmoud M., e Abdel A. Abdel-Rahman. "Estrogen enhances baroreflex control of heart rate in conscious ovariectomized rats". Canadian Journal of Physiology and Pharmacology 76, n. 4 (1 aprile 1998): 381–86. http://dx.doi.org/10.1139/y98-031.

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In previous studies, we have shown that the baroreflex control of heart rate is significantly attenuated in females compared with age-matched males. This study investigated the role of estrogen in the modulation of baroreflex function in conscious unrestrained rats. Baroreflex-mediated decreases in heart rate in response to increments in blood pressure evoked by phenylephrine were evaluated in conscious freely moving male and female Sprague-Dawley rats as well as in ovariectomized rats. The effect of a 2-day 17 beta -estradiol (50 µg ·kg-1 ·day-1, s.c.) or vehicle treatment on baroreflex sensitivity was investigated in ovariectomized rats. Intravenous bolus doses of phenylephrine (1-16 µg/kg) elicited dose-dependent pressor and bradycardic responses in all groups of rats. Regression analysis of the baroreflex curves relating increments in blood pressure to the associated heart rate responses revealed a significantly (p < 0.05) smaller baroreflex sensitivity in female compared with male rats (-1.22 ± 0.07 and -1.85 ± 0.15 beats ·min-1 ·mmHg-1, respectively), suggesting an attenuated baroreflex function in females. In age-matched ovariectomized rats, baroreflex sensitivity showed further reduction (-0.93 ± 0.02 beats ·min-1 ·mmHg-1). Treatment of ovariectomized rats with 17 beta -estradiol significantly (p < 0.05) enhanced the baroreflex sensitivity (-1.41 ± 0.16 beats ·min-1 ·mmHg-1) to a level that was slightly higher than that of sham-operated female rats. Furthermore, baroreflex sensitivity of ovariectomized estradiol-treated rats was not significantly different from that of age-matched male rats. The vehicle, on the other hand, had no effect on baroreflex sensitivity of ovariectomized rats. These data support our earlier findings that sexual dimorphism exists in baroreflex control of heart rate. More importantly, the present study provides experimental evidence that suggests a facilitatory role for estrogen in the modulation of baroreflex function.Key words: rat, gender, baroreflex sensitivity, 17 beta -estradiol, ovariectomy.

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Kawarabayashi, T., K. Yasunari, Y. Kanayama, K. Takeuchi e T. Takeda. "ERYTHROCYTE WATER CONTENT IN SPONTANEOUSLY HYPERTENSIVE RATS AND DOCA-SALT HYPERTENSIVE RATS". Clinical and Experimental Pharmacology and Physiology 13, n. 11-12 (dicembre 1986): 783–90. http://dx.doi.org/10.1111/j.1440-1681.1986.tb02382.x.

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Baka, Tomas, e Fedor Simko. "Ivabradine reversed nondipping heart rate in rats with l ‐ NAME ‐induced hypertension". Clinical and Experimental Pharmacology and Physiology 46, n. 6 (28 marzo 2019): 607–10. http://dx.doi.org/10.1111/1440-1681.13075.

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Félix, Bernadette, André Jean e Claude Roman. "Leptin inhibits swallowing in rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 291, n. 3 (settembre 2006): R657—R663. http://dx.doi.org/10.1152/ajpregu.00560.2005.

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Swallowing is under the control of premotoneurons located in the medullary solitary tract nucleus. Although rats with transected midbrain do not seek out food, they are able to ingest food present near the mouth, and acute food deprivation induces an increase in food intake. Leptin is a satiety signal that regulates feeding behavior. Because leptin receptors are found within the caudal brainstem, and because food intake is regulated in midbrain transected rats, this study tested the hypothesis that leptin is able to modify the activity of premotoneurons involved in swallowing. Leptin was microinjected at the subpostremal level of the medullary solitary tract nucleus in anesthetized Wistar rats. Electromyographic electrodes in sublingual muscles allowed recording of swallowing induced by stimulation of sensitive fibers of the superior laryngeal nerve. Repeated stimulation induced rhythmic swallowing. Microinjection of leptin (0.1 pg and 0.1 ng) in the swallowing center induced an inhibition of rhythmic swallowing (latency of <30 s) as shown by the reduced number and strength of electromyographic activities, which could last several minutes. The threshold of the leptin-induced inhibition was close to 0.1 pg. Interestingly, the inhibitory effect of leptin was not observed in leptin receptor-deficient Zucker rats. Here we show that, in Wistar rats, leptin already known to modulate the discharge of medullary solitary tract nucleus-sensitive neurons involved in satiety reflexes can also modify the activity of swallowing premotoneurons, thereby inhibiting an essential motor component of feeding behavior.

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Monson, C. B., S. L. Patterson, J. M. Horowitz e J. Oyama. "Thermoregulation in hypergravity-acclimated rats". Journal of Applied Physiology 67, n. 1 (1 luglio 1989): 383–89. http://dx.doi.org/10.1152/jappl.1989.67.1.383.

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To determine the effect of hypergravity acclimation on thermoregulation, core temperature (Tc), tail temperature (Tt), and O2 consumption (VO2) were measured in control rats (raised at 1 G) and in rats acclimated to 2.1 G. When the animals were exposed to a low ambient temperature of 9 degrees C, concurrently with a hypergravic field of 2.1 G, Tc of rats raised at 1 G fell markedly by approximately 6 degrees C (to 30.8 +/- 0.6 degrees C) while that of the rats raised at 2.1 G remained relatively constant (falling only approximately 1 degree C to 36.4 +/- 0.3 degrees C). Thus prior acclimation to a 2.1-G field enabled rats to maintain Tc when cold exposed in a 2.1-G field. To maintain Tc, thermogenic mechanisms were successfully activated in the 2.1-G-acclimated rats as shown by measurements of VO2. In contrast, VO2 measurements showed that rats reared at 1 G and then cold exposed at 2.1 G did not activate thermogenic mechanisms sufficiently to prevent a fall in Tc. In other experiments, rats acclimated to either 1 or 2.1 G were found to lack the ability to maintain their Tc when exposed to a 5.8-G field or when exposed to prolonged cold exposure at 1 G. Results are interpreted as showing that when placed in a 2.1-G field, rats acclimated to 2.1 G can more closely maintain their Tc near 37 degrees C when cold exposed than can rats acclimated to 1 G. However, this enhanced regulatory ability of 2.1-G-acclimated rats over 1.0-G-acclimated rats is restricted to 2.1-G fields and is not observed in 1.0- and 5.8-G fields.

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Şentürk, Ümit Kemal, Filiz Gündüz, Oktay Kuru, Mehmet R. Aktekin, Dijle Kipmen, Özlem Yalçin, Melek Bor-Küçükatay, Akin Yeşilkaya e Oğuz K. Başkurt. "Exercise-induced oxidative stress affects erythrocytes in sedentary rats but not exercise-trained rats". Journal of Applied Physiology 91, n. 5 (1 novembre 2001): 1999–2004. http://dx.doi.org/10.1152/jappl.2001.91.5.1999.

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Oxidant stress is one of the factors proposed to be responsible for damaged erythrocytes observed during and after exercise. The impact of exertional oxidant stress after acute exhaustive treadmill running on erythrocyte damage was investigated in sedentary (Sed) and exercise-trained (ET) rats treated with or without antioxidant vitamins C and E. Exhaustive exercise led to statistically significant increments in the levels of thiobarbituric acid-reactive substance (TBARS) and H2O2-induced TBARS in Sed rats and resulted in functional and structural alterations in erythrocytes (plasma hemoglobin concentrations, methemoglobin levels, and rise in osmotic fragility of erythrocytes with decrease in erythrocyte deformability). Administration of antioxidant vitamin for 1 mo before exhaustive exercises prevented lipid peroxidation (TBARS, H2O2-induced TBARS) in Sed rats without any functional or structural alterations in erythrocytes. Parameters indicating erythrocyte lipid peroxidation and deterioration after exhaustive exercise in rats trained regularly with treadmill running for 1 mo were not different from those in Sed controls. Erythrocyte lipid peroxidation (TBARS) increased in exhausted-ET rats compared with ET controls; however, the plasma hemoglobin, methemoglobin levels, and erythrocyte osmotic fragility and deformability did not differ. Exhaustive exercise-induced lipid peroxidation in ET rats on antioxidant vitamin treatment was prevented, whereas functional and structural parameters of erythrocytes were not different from those of the ET controls. We conclude that exertional oxidant stress contributed to erythrocyte deterioration due to exercise in Sed but not in ET rats.

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SKARPHEDINSSON, J. O., L. STAGE e P. THORÉN. "Cerebral function during hypotensive haemorrhage in spontaneously hypertensive rats and Wistar Kyoto rats". Acta Physiologica Scandinavica 128, n. 3 (novembre 1986): 445–52. http://dx.doi.org/10.1111/j.1748-1716.1986.tb07998.x.

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Hidayat, Rachmat, e Patricia Wulandari. "Anatomy and Physiology of Animal Model Rats in Biomedical Research". Biomedical Journal of Indonesia 7, n. 2 (12 marzo 2021): 265–69. http://dx.doi.org/10.32539/bji.v7i2.287.

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A distinguishing feature of rodents, including rats, is the absence of canines and thepresence of prominent incisors. Rats are monophydontic, meaning they grow one setof teeth in their lifetime. The enamel of the rodent incisor contains iron, which givesit its yellow-orange color. Rats are mammals and as such, possess many similaritieswith other mammals. Only the peculiarities of the rat’s anatomy are addressed. Malerats reach puberty at 40 - 60 days of age. Descent of the testes usually occursbetween days 30 - 60. Sperm counts vary by strain. The male rat has an os penis.Male rats have the following accessory sexual organs: ampulla, seminal vesicles,prostate, bulbourethral glands, coagulating glands, and preputial glands. Thecoagulating gland and prostatic and vesicular secretions are responsible for thecopulation plug, a firm plug deposited in the vagina of the female after copulation.(This plug, when found outside the female rat, is capsuleshaped and approximately5 mm long.) The male rat has no nipples. The adult male rat has a prominentscrotum and a longer anogenital distance than the female rat.

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Hwang, S., N. J. Lee, J. S. Hwang, B. C. Yang, G. S. Im, Y. G. Ko, E. W. Park, S. B. Park, J. K. Kang e H. H. Seong. "Effects of cloned-cattle meat on reproductive physiology in rats". Animal 4, n. 2 (2010): 218–23. http://dx.doi.org/10.1017/s1751731109990966.

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Arimura, K., Y. Murai, R. L. Rosales e S. Izumo. "Spinal roots of rats poisoned with methylmercury: Physiology and pathology". Muscle & Nerve 11, n. 7 (luglio 1988): 762–68. http://dx.doi.org/10.1002/mus.880110713.

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Soltis, R. P., e J. A. DiMicco. "GABAA and excitatory amino acid receptors in dorsomedial hypothalamus and heart rate in rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 260, n. 1 (1 gennaio 1991): R13—R20. http://dx.doi.org/10.1152/ajpregu.1991.260.1.r13.

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We have previously shown that microinjection of drugs that interfere with the function of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) into the hypothalamus produces cardiorespiratory and behavioral changes resembling those seen in emotional stress. The purpose of this study was to determine whether excitatory amino acids (EAAs) can produce a cardiovascular response similar to that caused by the GABAA receptor antagonist bicuculline methiodide (BMI) when microinjected at the same hypothalamic site in urethan-anesthetized rats and to clarify the precise locus of action of these agents. N-methyl-D-aspartic acid (NMDA, 0.68-6.8 pmol/50 nl) and kainic acid (KA, 0.47-4.7 pmol/50 nl) produced dose-related increases in heart rate and blood pressure when injected at sites in the dorsomedial hypothalamus reactive to BMI (20 pmol/50 nl). Higher doses of NMDA (68 pmol), however, failed to elicit consistent increases in heart rate and blood pressure when injected at these same sites. The effects of NMDA were selectively blocked by the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid, whereas the effects of KA were selectively blocked by the non-NMDA EAA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. These results demonstrate that 1) blockade of inhibitory amino acid receptors or stimulation of EAA receptors in the dorsomedial nucleus of the hypothalamus produces tachycardic and pressor responses in urethan-anesthetized rats and 2) use of high doses of EAAs may be an unreliable method of evoking local neuronal excitation in certain regions of the central nervous system.

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Soltis, R. P., e J. A. DiMicco. "Interaction of hypothalamic GABAA and excitatory amino acid receptors controlling heart rate in rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 261, n. 2 (1 agosto 1991): R427—R433. http://dx.doi.org/10.1152/ajpregu.1991.261.2.r427.

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We have previously shown that microinjection of drugs that impair gamma-aminobutyric acid (GABA)-mediated synaptic inhibition into the dorsomedial hypothalamus (DMH) of rats generates cardiovascular and behavioral changes that mimic the response to stress. The purpose of this study was to examine the role of excitatory amino acid (EAA) receptors in the DMH in generating the cardiovascular changes caused by withdrawal of local GABAergic inhibition in urethan-anesthetized rats. Local treatment of the DMH with the nonselective EAA antagonist kynurenic acid blocked or reversed the increases in heart rate and blood pressure caused by microinjection of the GABAA antagonists bicuculline methiodide (BMI) or picrotoxin into the same region. Conversely, similar injection of xanthurenic acid, a structural analogue of kynurenic acid without significant effects on EAA receptors, did not significantly alter the cardiovascular changes produced by either GABAA antagonist. The tachycardic effects of BMI were also attenuated by injection of either the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid or the non-NMDA EAA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. When the two EAA receptor antagonists were combined, their effects to suppress the BMI-induced tachycardia were additive. These findings suggest that the cardiovascular effects caused by blockade of GABAergic inhibition in the DMH of the rat are dependent on activation of local NMDA and non-NMDA EAA receptors.

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Anderson, Joseph C., Robert C. Molthen, Christopher A. Dawson, Steve T. Haworth, Joseph L. Bull, Matthew R. Glucksberg e James B. Grotberg. "Effect of ventilation rate on instilled surfactant distribution in the pulmonary airways of rats". Journal of Applied Physiology 97, n. 1 (luglio 2004): 45–56. http://dx.doi.org/10.1152/japplphysiol.00609.2003.

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Liquid can be instilled into the pulmonary airways during medical procedures such as surfactant replacement therapy, partial liquid ventilation, and pulmonary drug delivery. For all cases, understanding the dynamics of liquid distribution in the lung will increase the efficacy of treatment. A recently developed imaging technique for the study of real-time liquid transport dynamics in the pulmonary airways was used to investigate the effect of respiratory rate on the distribution of an instilled liquid, surfactant, in a rat lung. Twelve excised rat lungs were suspended vertically, and a single bolus (0.05 ml) of exogenous surfactant (Survanta, Ross Laboratories, Columbus, OH) mixed with radiopaque tracer was instilled as a plug into the trachea. The lungs were ventilated with a 4-ml tidal volume for 20 breaths at one of two respiratory rates: 20 or 60 breaths/min. The motion of radiodense surfactant was imaged at 30 frames/s with a microfocal X-ray source and an image intensifier. Dynamics of surfactant distribution were quantified for each image by use of distribution statistics and a homogeneity index. We found that the liquid distribution depended on the time to liquid plug rupture, which depends on ventilation rate. At 20 breaths/min, liquid was localized in the gravity-dependent region of the lung. At 60 breaths/min, the liquid coated the airways, providing a more vertically uniform liquid distribution.

26

Johansson, Maria E., Irene J. Andersson, Camilla Alexanderson, Ole Skøtt, Agneta Holmäng e Göran Bergström. "Hyperinsulinemic rats are normotensive but sensitized to angiotensin II". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 294, n. 4 (aprile 2008): R1240—R1247. http://dx.doi.org/10.1152/ajpregu.00493.2007.

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The effect of insulin on blood pressure (BP) is debated, and an involvement of an activated renin-angiotensin aldosterone system (RAAS) has been suggested. We studied the effect of chronic insulin infusion on telemetry BP and assessed sympathetic activity and dependence of the RAAS. Female Sprague-Dawley rats received insulin (2 units/day, INS group, n = 12) or insulin combined with losartan (30 mg·kg−1·day−1, INS+LOS group, n = 10), the angiotensin II receptor antagonist, for 6 wk. Losartan-treated (LOS group, n = 10) and untreated rats served as controls ( n = 11). We used telemetry to measure BP and heart rate (HR), and acute ganglion blockade and air-jet stress to investigate possible control of BP by the sympathetic nervous system. In addition, we used myograph technique to study vascular function ex vivo. The INS and INS+LOS groups developed euglycemic hyperinsulinemia. Insulin did not affect BP but increased HR (27 beats/min on average). Ganglion blockade reduced mean arterial pressure (MAP) similarly in all groups. Air-jet stress did not increase sympathetic reactivity but rather revealed possible blunting of the stress response in hyperinsulinemia. Chronic losartan markedly reduced 24-h-MAP in the INS+LOS group (−38 ± 1 mmHg P < 0.001) compared with the LOS group (−18 ± 1 mmHg, P ≤ 0.05). While insulin did not affect vascular function per se, losartan improved endothelial function in the aorta of insulin-treated rats. Our results raise doubt regarding the role of hyperinsulinemia in hypertension. Moreover, we found no evidence that insulin affects sympathetic nervous system activity. However, chronic losartan treatment revealed an important interaction between insulin and RAAS in BP control.

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Mizuno, Masaki, Toru Kawada, Atsunori Kamiya, Tadayoshi Miyamoto, Shuji Shimizu, Toshiaki Shishido, Scott A. Smith e Masaru Sugimachi. "Dynamic characteristics of heart rate control by the autonomic nervous system in rats". Experimental Physiology 95, n. 9 (18 giugno 2010): 919–25. http://dx.doi.org/10.1113/expphysiol.2010.053090.

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28

Shi, Zhang‐Jing, Ming Cheng, Ying‐Cai Liu, Xin‐Rong Fan, Yi Zhang e Yan Wei. "Effect of chronic intermittent hypobaric hypoxia on heart rate variability in conscious rats". Clinical and Experimental Pharmacology and Physiology 47, n. 1 (12 settembre 2019): 60–66. http://dx.doi.org/10.1111/1440-1681.13170.

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29

Head, Geoffrey A., e Michael A. Adams. "CHARACTERIZATION OF THE BARORECEPTOR HEART RATE REFLEX DURING DEVELOPMENT IN SPONTANEOUSLY HYPERTENSIVE RATS". Clinical and Experimental Pharmacology and Physiology 19, n. 8 (agosto 1992): 587–97. http://dx.doi.org/10.1111/j.1440-1681.1992.tb00509.x.

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30

Kubota, Y., S. Kagota, Y. Tada, N. Nejime, K. Nakamura, M. Kunitomo, K. Umegaki e K. Shinozuka. "GINKGO BILOBA EXTRACT CAUSES DECREASE IN HEART RATE IN AGED SPONTANEOUSLY HYPERTENSIVE RATS". Clinical and Experimental Pharmacology and Physiology 34, s1 (novembre 2007): S49—S50. http://dx.doi.org/10.1111/j.1440-1681.2007.04776.x.

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31

Spencer, Sarah J., Abdeslam Mouihate, Michael A. Galic, Shaun L. Ellis e Quentin J. Pittman. "Neonatal immune challenge does not affect body weight regulation in rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, n. 2 (agosto 2007): R581—R589. http://dx.doi.org/10.1152/ajpregu.00262.2007.

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Abstract (sommario):

The perinatal environment plays a crucial role in programming many aspects of adult physiology. Myriad stressors during pregnancy, from maternal immune challenge to nutritional deficiency, can alter long-term body weight set points of the offspring. In light of the increasing concern over body weight issues, such as obesity and anorexia, in modern societies and accumulating evidence that developmental stressors have long-lasting effects on other aspects of physiology (e.g., fever, pain), we explored the role of immune system activation during neonatal development and its impact on body weight regulation in adulthood. Here we present a thorough evaluation of the effects of immune system activation (LPS, 100 μg/kg ip) at postnatal days 3, 7, or 14 on long-term body weight, adiposity, and body weight regulation after a further LPS injection (50 μg/kg ip) or fasting and basal and LPS-induced circulating levels of the appetite-regulating proinflammatory cytokine leptin. We show that neonatal exposure to LPS at various times during the neonatal period has no long-term effects on growth, body weight, or adiposity. We also observed no effects on body weight regulation in response to a short fasting period or a further exposure to LPS. Despite reductions in circulating leptin levels in response to LPS during the neonatal period, no long-term effects on leptin were seen. These results convincingly demonstrate that adult body weight and weight regulation are, unlike many other aspects of adult physiology, resistant to programming by a febrile-dose neonatal immune challenge.

32

Brouillard, Charly, Pascal Carrive, Françoise Camus, Jean-Jacques Bénoliel, Thomas Similowski e Caroline Sévoz-Couche. "Long-lasting bradypnea induced by repeated social defeat". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 311, n. 2 (1 agosto 2016): R352—R364. http://dx.doi.org/10.1152/ajpregu.00021.2016.

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Repeated social defeat in the rat induces long-lasting cardiovascular changes associated with anxiety. In this study, we investigated the effects of repeated social defeat on breathing. Respiratory rate was extracted from the respiratory sinus arrhythmia (RSA) peak frequency of the ECG in rats subjected to social defeat for 4 consecutive days. Respiratory rate was recorded under anesthesia 6 days (D+10) or 26 days (D+30) after social defeat. At D+10, defeated (D) rats spent less time in the open arms of the elevated plus maze test, had heavier adrenal glands, and displayed bradypnea, unlike nondefeated animals. At D+30, all signs of anxiety had disappeared. However, one-half of the rats still displayed bradypnea (DL rats, for low respiratory rate indicated by a lower RSA frequency), whereas those with higher respiratory rate (DH rats) had recovered. Acute blockade of the dorsomedial hypothalamus (DMH) or nucleus tractus solitarii (NTS) 5-HT3 receptors reversed bradypnea in all D rats at D+10 and in DL rats at D+30. Respiratory rate was also recorded in conscious animals implanted with radiotelemetric ECG probes. DH rats recovered between D+10 and D+18, whereas DL rats remained bradypneic until D+30. In conclusion, social stress induces sustained chronic bradypnea mediated by DMH neurons and NTS 5-HT3 receptors. These changes are associated with an anxiety-like state that persists until D+10, followed by recovery. However, bradypnea may persist in one-half of the population up until D+30, despite apparent recovery of the anxiety-like state.

33

Cui, Yimin, Koh-Ichi Sugimoto, Yoshiko Kawai, Toshiaki Sudoh, Munekazu Gemba e Akio Fujimura. "Chronotoxicity of Nedaplatin in Rats". Chronobiology International 21, n. 4-5 (gennaio 2004): 601–11. http://dx.doi.org/10.1081/cbi-120039814.

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34

Todorova, M., M. Baleva, K. Nikolov, H. Higashino e Z. Kamenov. "Anticardiolipin Antibodies In Spontaneously Hypertensive Rats (Shr), Stroke-Prone Shr And Normal Wistar Rats". Clinical and Experimental Pharmacology and Physiology 27, n. 9 (14 settembre 2000): 705–8. http://dx.doi.org/10.1046/j.1440-1681.2000.03316.x.

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35

Simpson, Jeremy A., Keith R. Brunt, Christine P. Collier e Steve Iscoe. "Hyperinflation-induced cardiorespiratory failure in rats". Journal of Applied Physiology 107, n. 1 (luglio 2009): 275–82. http://dx.doi.org/10.1152/japplphysiol.91342.2008.

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Abstract (sommario):

We previously showed that severe inspiratory resistive loads cause acute (<1 h) cardiorespiratory failure characterized by arterial hypotension, multifocal myocardial infarcts, and diaphragmatic fatigue. The mechanisms responsible for cardiovascular failure are unknown, but one factor may be the increased ventricular afterload caused by the large negative intrathoracic pressures generated when breathing against an inspiratory load. Because expiratory threshold loads increase intrathoracic pressure and decrease left ventricular afterload, we hypothesized that anesthetized rats forced to breathe against such a load would experience only diaphragmatic failure. Loading approximately doubled end-expiratory lung volume, halved respiratory frequency, and caused arterial hypoxemia and hypercapnia, respiratory acidosis, and increased inspiratory drive. Although hyperinflation immediately reduced the diaphragm's mechanical advantage, fatigue did not occur until near load termination. Mean arterial pressure progressively fell, becoming significant (cardiovascular failure) midway through loading despite tachycardia. Loading was terminated (endurance 125 ± 43 min; range 82–206 min) when mean arterial pressure dropped below 50 mmHg. Blood samples taken immediately after load termination revealed hypoglycemia, hyperkalemia, and cardiac troponin T, the last indicating myocardial injury that was, according to histology, mainly in the right ventricle. This damage probably reflects a combination of decreased O2 delivery (decreased venous return and arterial hypoxemia) and greater afterload due to hyperinflation-induced increase in pulmonary vascular resistance. Thus, in rats breathing at an increased end-expiratory lung volume, cardiorespiratory, not just respiratory, failure still occurred. Right heart injury and dysfunction may contribute to the increased morbidity and mortality associated with acute exacerbations of obstructive airway disease.

36

Montcalm-Smith, E. A., R. M. McCarron, W. R. Porter, R. S. Lillo, J. T. Thomas e C. R. Auker. "Acclimation to decompression sickness in rats". Journal of Applied Physiology 108, n. 3 (marzo 2010): 596–603. http://dx.doi.org/10.1152/japplphysiol.00596.2009.

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Protection against decompression sickness (DCS) by acclimation to hyperbaric decompression has been hypothesized but never proven. We exposed rats to acclimation dives followed by a stressful “test” dive to determine whether acclimation occurred. Experiments were divided into two phases. Phase 1 rats were exposed to daily acclimation dives of hyperbaric air for 30 min followed by rapid decompression on one of the following regimens: 70 ft of seawater (fsw) for 9 days (L70), 70 fsw for 4 days (S70), 40 fsw for 9 days (L40), 40 fsw for 4 days (S40), or unpressurized sham exposure for 9 days (Control). On the day following the last exposure, all were subjected to a “test” dive (175 fsw, 60 min, rapid decompression). Both L70 and S70 rats had significantly lower incidences of DCS than Control rats (36% and 41% vs. 62%, respectively). DCS incidences for the other regimens were lower than in Control rats but without statistical significance. Phase 2 used the most protective regimen from phase 1 (L70); rats were exposed to L70 or a similar regimen with a less stressful staged decompression. Another group was exposed to a single acclimation dive (70 fsw/30 min) on the day before the test dive. We observed a nonsignificant trend for the rapidly decompressed L70 dives to be more protective than staged decompression dives (44% vs. 51% DCS incidence). The single acclimation dive regimen did not provide protection. We conclude that protection against DCS can be attained with acclimating exposures that do not themselves cause DCS. The deeper acclimation dive regimens (70 fsw) provided the most protection.

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Moran, M. M., R. R. Roy, C. E. Wade, B. J. Corbin e R. E. Grindeland. "Size constraints of telemeters in rats". Journal of Applied Physiology 85, n. 4 (1 ottobre 1998): 1564–71. http://dx.doi.org/10.1152/jappl.1998.85.4.1564.

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Abstract (sommario):

This study was designed to determine the maximum-size subcutaneous telemeter that would enable long-term and multichannel data collection in a 170-g rat for 90 days. In phase 1, rats with implants weighing 5 (2.5 cm3), 15 (7.5 cm3), 25 (12.5 cm3), 35 (17.5 cm3), or 45 (22.5 cm3) g were compared with sham-operated (SOC) and nonoperated (NOC) control animals. Severe skin lesions, seromas, and lower growth rates were observed in rats having implants ≥35 g. Thus, in phase 2, rats implanted with 23.5 g (17.5 cm3; 11-g active telemeter and 12.5-g implant) were compared with rats implanted with 11 g (6 cm3; telemeter only) and with the SOC and NOC groups. No differences were found among implanted groups in mean arterial pressure (MAP), heart rate (HR), subcutaneous temperature, or spontaneous activity under standard housing conditions. All groups were more active and had a higher MAP during the dark than the light phase of the daily cycle. During 2 h of cold exposure (3°C), both telemetered groups exhibited similar changes in HR, MAP, temperature, and activity levels. Adrenal glands were larger in the 23.5-g group (51 ± 1.6 mg) than in the SOC (46 ± 1.0 mg) and the NOC groups (41 ± 2.0 mg). No other significant differences were found in organ, muscle, or bone weights. These data verify the feasibility of using 23.5-g (17.5 cm3) subcutaneous telemeters for chronic recordings in young adult rats.

38

Wilson, K. M., e M. J. Fregly. "Angiotensin II-induced hypothermia in rats". Journal of Applied Physiology 58, n. 2 (1 febbraio 1985): 534–43. http://dx.doi.org/10.1152/jappl.1985.58.2.534.

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Systemic administration of angiotensin II (ANG II) (200 micrograms/kg sc) to the rat induced a hypothermic response that was characterized within 12 min by a reduction in the rate of O2 consumption, vasodilation of the tail, and a 1.3 degrees C fall in colonic temperature. Administration of ANG II in doses ranging from 10 to 200 micrograms/kg resulted in a decrease in colonic and an increase in tail skin temperature. Angiotensin I (ANG I) (200 micrograms/kg sc) induced a similar hypothermic response which was abolished by pretreatment with the ANG I-converting enzyme inhibitor, captopril (35 mg/kg ip). The interaction of ANG II with cholinergic and adrenergic pathways was evaluated to determine possible mechanisms. Treatment with ANG II (200 micrograms/kg sc) and propranolol, a beta-adrenoceptor antagonist (6 mg/kg ip), resulted in a greater depression of colonic temperature (Tco) than was observed with ANG II alone but did not affect the increase in tail skin temperature (Tsk) accompanying administration of ANG II. When ANG II was administered in combination with the beta-adrenergic agonist, isoproterenol (50 micrograms/kg ip), Tco remained at control levels, whereas an enhancement of the ANG II-induced increase in Tsk occurred. Administration of ANG II in combination with atropine sulfate (6 mg/kg ip), a muscarinic receptor antagonist which crosses the blood-brain barrier, significantly reduced the extent of the fall in Tco without affecting the increase in Tsk. The combined treatment of ANG II and the quaternary analogue, atropine methyl nitrate (3.25 mg/kg ip), which does not cross the blood-brain barrier, failed to affect the hypothermic responses to ANG II. These results suggest that the hypothermic responses to ANG II may be mediated through a central cholinergic pathway and possibly influenced by an adrenergic component. The inability of both adrenergic and cholinergic blockers to affect the vasodilatory response of the tail of the rat to administration of ANG II suggests that the mechanisms subserving heat production can be blocked independently of those subserving heat loss.

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Grigson, P. S., J. M. Kaplan, M. F. Roitman, R. Norgren e H. J. Grill. "Reward comparison in chronic decerebrate rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, n. 2 (1 agosto 1997): R479—R486. http://dx.doi.org/10.1152/ajpregu.1997.273.2.r479.

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The simultaneous contrast paradigm was used to evaluate responsiveness to a low (0.05 M) and a high (0.5 M) concentration of sucrose under two conditions in intact and chronic decerebrate rats. In one condition the low concentration was presented on one day and the high concentration on another. In the other condition presentation of the two concentration was alternated within the same daily session. In each case there was a total of 40 trials/day during which the stimulus was delivered intraorally for 2 s at a rate of 1.5 ml/min with a 30-s intertrial interval. The results showed that the intact rats always licked more for the high than for the low concentration of sucrose but that the magnitude of the effect was larger when given the opportunity to compare the two concentrations within the same daily session. The decerebrate rats produced a similar pattern, but the concentration effect was evident only when the stimuli were alternated within the same daily session. These data stand as the first evidence that the isolated caudal brain stem is adequate for the expression of a behavior that depends on comparison processes involving short-term memory.

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Rowland, Neil E., Annie Morien, Mircea Garcea e Melvin J. Fregly. "Aging and fluid homeostasis in rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 273, n. 4 (1 ottobre 1997): R1441—R1450. http://dx.doi.org/10.1152/ajpregu.1997.273.4.r1441.

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Abstract (sommario):

The capacity of aging rats to defend body fluid homeostasis in response to a variety of dipsogenic and natriorexigenic stimuli was assessed. Male and female rats of both the Fischer 344 (FR) and Sprague-Dawley (SD) strains were used and tested at target ages of ∼5, 10, 15, and 20 mo in both longitudinal and cross-sectional studies. There were no consistent age-related declines in water intake in response to water deprivation or acute administration of hypertonic NaCl; angiotensin (ANG) I, II, III; or isoproterenol. Likewise, there were no major impairments in either urinary excretion of the hypertonic NaCl load or excretion of water or hypotonic NaCl loads, although the latter were excreted more slowly in the older cohorts. The preference/aversion functions for NaCl solutions differed between SD and FR rats, but did not change with age except in male FR rats that lost their aversion to dilute NaCl at 20 mo of age. Intake of hypotonic NaCl solution after acute sodium depletion (furosemide treatment) showed a partial decline with age, and the older rats sustained larger estimated sodium deficits after a 6-h repletion period. A more complete age-related decline was observed in the intake of hypertonic NaCl stimulated by chronic dietary administration of a kininase II inhibitor (ramipril). Male rats of 15–20 mo of age showed no ramipril-induced sodium appetite. Brain ANG II receptor density, determined by autoradiography, declined by almost 50% in the paraventricular nucleus at 20 mo of age and declined slightly in the organum vasculosum laminae terminalis but did not decline in either the supraoptic nucleus or subfornical organ. Thus the major deficits in fluid intake in aging rats are related to salt appetite; the mechanism was not identified definitively.

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Tomohiro, A., S. Kimura, H. He, Y. Fujisawa, A. Nishiyama, K. Kiyomoto, Y. Aki, T. Tamaki e Y. Abe. "Regional blood flow in Dahl-Iwai salt-sensitive rats and the effects of dietary L-arginine supplementation". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 272, n. 4 (1 aprile 1997): R1013—R1019. http://dx.doi.org/10.1152/ajpregu.1997.272.4.r1013.

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The purpose of the present study was to determine 1) whether different organs undergo similar increase in vascular resistance in Dahl-Iwai salt-sensitive (S) rats, and 2) the effects of chronic oral L-arginine supplementation on the regional hemodynamics in S rats. Male 6-wk-old S rats and salt-resistant (R) rats were maintained on an 8% NaCl chow for 4 wk. One group (S or R rats) was maintained on tap water and the other group (S/Arg or R/Arg rats) received tap water containing L-arginine at a concentration of 1.5%. Organ blood flow and cardiac output were measured with microspheres in the conscious condition. Mean blood pressure in S, S/Arg, R, and R/Arg rats was 159 +/- 5, 138 +/- 3, 111 +/- 4, and 112 +/- 4 mmHg, respectively. Urinary excretion of protein and albumin in S/Arg rats was significantly suppressed compared with S rats. Concerning regional hemodynamics, the flow rate of the kidney was lower in S rats than in R rats, but there were no differences between S and R rats in the flow rates of the brain, heart, lung, liver, spleen, intestine, skeletal muscle, and skin. Thus the renal blood flow was solely reduced in S rats on a high-salt diet. The flow rate of the kidney in S/Arg rats was maintained at a higher level compared with that of S rats. L-Arginine treatment tended to produce a recovery in the urinary excretion of guanosine 3',5'-cyclic monophosphate in S rats, but had no effect in R rats. Thus the supplementation of L-arginine prevented the increase in blood pressure in S rats on a high-salt diet and normalized the abnormality of renal hemodynamics accompanying salt-induced hypertension.

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Alexander, N., S. Melmed e M. Morris. "Suppressed serum prolactin in sinoaortic-denervated rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 252, n. 2 (1 febbraio 1987): R290—R293. http://dx.doi.org/10.1152/ajpregu.1987.252.2.r290.

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We investigated the effect of arterial baroreceptor deafferentation on serum and pituitary prolactin (PRL) and on catecholamines in median eminence (ME) and anterior and posterior pituitaries. Male Wistar rats were sinoaortic denervated (SAD) or sham operated (SO). Three days after surgery serum prolactin, measured by radioimmunoassay, was suppressed in SAD rats (-54%, P less than 0.05), and dopamine (DA) and norepinephrine (NE) concentrations, measured by radioenzymatic or high-performance liquid chromatography electron capture methods, were significantly reduced in ME of SAD rats (NE, -54% P less than 0.005 and DA, -56% P less than 0.001). Simultaneously, anterior pituitary of SAD rats had significant increases in both catecholamines, whereas posterior pituitary showed no changes. Four hours after surgery serum PRL was also reduced (-40%, P less than 0.05) in SAD rats, but no changes in ME catecholamines were found. Mean arterial pressure (MAP) and heart rate were measured before and after injection of bromocriptine (0.5 mg/kg ip) in SAD and SO rats 3 days after surgery. Bromocriptine markedly suppressed serum PRL in both groups and reduced MAP from 144 +/- 10 to 84 +/- 5 and from 116 +/- 2 to 99 +/- 3 in SAD and SO rats, respectively; heart rate was reduced in SAD rats. We conclude that the SAD rat is a model of hypertension with suppressed serum PRL and that interruption of arterial baroreceptor nerves suppresses PRL secretion probably by modulating tuberoinfundibular turnover of catecholamines.

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Asarian, Lori, e Nori Geary. "Sex differences in the physiology of eating". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, n. 11 (1 dicembre 2013): R1215—R1267. http://dx.doi.org/10.1152/ajpregu.00446.2012.

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Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

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Wade, Brittany, Galina Petrova e David L. Mattson. "Role of immune factors in angiotensin II-induced hypertension and renal damage in Dahl salt-sensitive rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 314, n. 3 (1 marzo 2018): R323—R333. http://dx.doi.org/10.1152/ajpregu.00044.2017.

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Abstract (sommario):

The present study assessed the importance of immunity in angiotensin (ANG) II (5 ng·kg−1·min−1 iv)-mediated hypertension in Dahl salt-sensitive (SS) rats and SS rats deficient in T and B lymphocytes (SSRag1−/−) fed a 0.4% NaCl diet. Baseline mean arterial blood pressure (MAP) was not different between groups. ANG II infusion significantly increased MAP in both groups, although MAP increased more rapidly in SS rats, and the maximal MAP achieved was significantly greater in SS than SSRag1−/− rats (190 ± 3 vs. 177 ± 3 mmHg) after 12 days. Renal damage, as assessed by albumin excretion rate, was significantly increased after 12 days of ANG lI infusion in SS (from 32 ± 4 to 81 ± 9 mg/day) and SSRag1−/− (from 12 ± 2 to 51 ± 8 mg/day) rats; albumin excretion rate was significantly different between SS and SSRag1−/− rats at all points measured. After 9 days of recovery from ANG II, MAP was decreased to a greater extent in SSRag1−/− than SS rats (143 ± 5 vs. 157 ± 8 mmHg) compared with the peak MAP during ANG II infusion. At this same time point, albumin excretion rate was significantly lower in SSRag1−/− than SS rats (42 ± 8 vs. 66 ± 7 mg/day). Further studies demonstrated an increase in CD45+ total leukocytes, CD11b/c+ macrophages/monocytes, and CD3+ T cells in kidneys of ANG II- compared with vehicle-treated SS rats. The present data suggest that infiltrating T cells in the kidney exacerbate renal damage in ANG II-induced hypertension in SS rats maintained on a 0.4% NaCl diet, similar to results observed with a salt stimulus in SS rats.

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Contreras, Robert J., e Jennifer L. Studley. "Amiloride alters lick rate responses to NaCl and KCl in rats". Chemical Senses 19, n. 3 (1994): 219–29. http://dx.doi.org/10.1093/chemse/19.3.219.

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46

Dickhout, Jeffrey G., e Robert M. K. W. Lee. "Blood pressure and heart rate development in young spontaneously hypertensive rats". American Journal of Physiology-Heart and Circulatory Physiology 274, n. 3 (1 marzo 1998): H794—H800. http://dx.doi.org/10.1152/ajpheart.1998.274.3.h794.

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Abstract (sommario):

The course of hypertension development in young spontaneously hypertensive rats (SHR) was studied by the measurement of changes in systolic blood pressure (BP), body weight, and heart rate (HR) at 2, 3, 4, and 6 wk of age. To achieve this, we compared inbreeding lines of SHR and Wistar-Kyoto rats (WKY) to determine if differences in BP, body weight, or HR were present among inbreeding lines of the same strain or between strains. The effect of these differences on the eventual level of BP was then assessed. We found that BP began to diverge between SHR and WKY at 4 wk of age. Significant differences in systolic BP (24 mmHg) between SHR inbreeding lines at 4 wk of age did not affect the BP at 8 wk (172 vs. 170 mmHg). Pulse pressure was significantly higher in SHR than in WKY at 4 wk of age. HR was elevated in SHR over age-matched WKY at 3 wk of age and positively correlated to the level of BP attained by individual animals at 6 wk ( P = 0.037). Moreover, WKY inbreeding lines showing elevated HR developed higher BP (145 vs. 127 mmHg) at 10–12 and 20 wk of age. The prehypertensive tachycardia in SHR was investigated further and found to result from an increased intrinsic HR. Because HR at 3 wk is a genetic trait that can be partitioned into inbreeding lines, and inbreeding lines most expressive of this trait showed the highest eventual BP, we conclude that prehypertensive tachycardia may be an important first step during hypertension development in SHR. Moreover, early elevations in HR are highly predictive ( r = 0.41) of hypertension occurrence in the animal population studied.

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Takezawa, H., H. Hayashi, H. Sano, H. Saito e S. Ebihara. "Circadian and estrous cycle-dependent variations in blood pressure and heart rate in female rats". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 267, n. 5 (1 novembre 1994): R1250—R1256. http://dx.doi.org/10.1152/ajpregu.1994.267.5.r1250.

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To determine whether cardiovascular functions are controlled by the endogenous circadian system and whether they change with the estrous cycle in female rats, we measured mean arterial pressure (MAP), heart rate (HR), and spontaneous activity (ACT) of female rats using an implantable radiotelemetry device and a computerized data-collecting system. Under a 12:12-h light-dark (LD) cycle, these parameters exhibited daily rhythms that were entrained to the photic cycle. The patterns of the daily rhythms varied with estrous cycles, and variations were particularly marked in the proestrous stage. During the dark period of this stage, ACT levels were significantly higher, but HR was significantly lower than in other stages. Although the peak MAP occurred within 2 h after the onset of the dark phase in three of the estrous stages, it occurred around midnight in the proestrous stage. Such estrous cycle-dependent variations were eliminated by ovariectomy. The implantation of 17 beta-estradiol produced a gradual increase in MAP and an abrupt decrease in HR. During constant darkness, all three parameters were free running, maintaining the same internal phase relationships with each other as during LD cycles. These results indicate that daily variations in these parameters were controlled by the endogenous circadian oscillating system, that they vary with the estrous cycle in female rats, and that estrogen may be responsible for these estrous cycle-dependent variations.

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Sheng, H. P., e R. A. Huggins. "Tritiated water as a measure of body water in immature rats growing at different rates". Journal of Applied Physiology 66, n. 1 (1 gennaio 1989): 476–80. http://dx.doi.org/10.1152/jappl.1989.66.1.476.

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Rats were reared from birth in litters of 4, 10, and 16 to achieve different growth rates. Pups in the litters of 16 had no access to rat chow until days 21–28, when chow was made available to one of the litters to induce catch-up growth. Total body water was estimated by tritiated water (TBWHTO) on days 7, 14, 21, and 28 and then calculated from desiccation (TBWdes). TBWHTO was consistently larger than TBWdes for all groups. Differences were 10.9–16.9% on day 7 and 3.7–6.4% on day 28. On day 28, percent difference was higher in the slower-growing than the faster-growing groups. Nonaqueous hydrogen exchange was determined from tritium activity in the dried carcass. Less than 1% of the injected tritium exchanged with nonaqueous hydrogen during the equilibration period. Thus differences between TBWHTO and TBWdes in the younger animals could not be accounted for by nonaqueous hydrogen exchange but may have resulted from a larger loss of injected tritium, possibly in insensible water.

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Corman, B., S. Chami-Khazraji, J. Schaeverbeke e J. B. Michel. "Effect of feeding on glomerular filtration rate and proteinuria in conscious aging rats". American Journal of Physiology-Renal Physiology 255, n. 2 (1 agosto 1988): F250—F256. http://dx.doi.org/10.1152/ajprenal.1988.255.2.f250.

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Food intake increases glomerular filtration and proteinuria in adult rats. That this postprandial hyperfiltration could be age dependent was investigated in 3-, 10-, 20-, and 30-mo-old rats. Glomerular filtration rate and protein excretion were measured in fed or 24 h fasted conscious animals. In the 3-mo-old rats food ingestion increased renal filtration by 45% from 1.17 +/- 0.08 to 1.73 +/- 0.11 ml.min-1.g kidney wt-1 (n = 6). As the animals became older, the differences between fed and fasted periods became smaller: in 30-mo-old rats glomerular filtration rate was 0.85 +/- 0.03 and 1.01 +/- 0.06 ml.min-1.g kidney wt-1 (n = 6) in fasted and fed conditions, respectively. Proteinuria, which was mainly albuminuria, increased slightly with age and was more markedly reduced by acute food restriction in the 30-mo-old than in the 3-mo-old rats. Because the renin-angiotensin system activity decreases with age, its role in postprandial hyperfiltration was assessed by measuring glomerular filtration in 3-mo-old animals whose angiotensin II converting-enzyme activity was chronically inhibited by daily administration of perindopril. In such experimental conditions there was no longer a difference in renal filtration between fed and fasted rats. These data indicate that 1) postprandial increase in glomerular filtration is to some extent related to the renin-angiotensin system activity; 2) short-term reduction of food intake reduces proteinuria even in senescent rats, although the feeding dependence of the glomerular filtration is blunted with age.

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Besseling, Paul J., Tobias T. Pieters, Isabel T. N. Nguyen, Petra M. de Bree, Nel Willekes, Adele H. Dijk, Dominique M. Bovée et al. "A plasma creatinine- and urea-based equation to estimate glomerular filtration rate in rats". American Journal of Physiology-Renal Physiology 320, n. 3 (1 marzo 2021): F518—F524. http://dx.doi.org/10.1152/ajprenal.00656.2020.

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