scholarly journals Influence of light/dark cycle and orexins on breathing control in green iguanas (Iguana iguana)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Elisa M. Fonseca ◽  
Mariane C. Vicente ◽  
Stephanie Fournier ◽  
Richard Kinkead ◽  
Kênia C. Bícego ◽  
...  
Keyword(s):  
Breathing Pattern ◽  
Active Phase ◽  
Hypothalamic Nucleus ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Orexin A ◽  
Breathing Control ◽  
Green Iguanas ◽  
Cyclic Changes

AbstractLight/dark cycle affects the physiology of vertebrates and hypothalamic orexin neurons (ORX) are involved in this function. The breathing pattern of the green iguana changes from continuous to episodic across the light/dark phases. Since the stimulatory actions of ORX on breathing are most important during arousal, we hypothesized that ORX regulates changes of breathing pattern in iguanas. Thus, we: (1) Localized ORX neurons with immunohistochemistry; (2) Quantified cyclic changes in plasma orexin-A levels by ELISA; (3) Compared breathing pattern at rest and during hypoxia and hypercarbia; (4) Evaluated the participation of the ORX receptors in ventilation with intracerebroventricular microinjections of ORX antagonists during light and dark phases. We show that the ORX neurons of I. iguana are located in the periventricular hypothalamic nucleus. Orexin-A peaks during the light/active phase and breathing parallels these cyclic changes: ventilation is higher during the light phase than during the dark phase. However, inactivation of ORX-receptors does not affect the breathing pattern. Iguanas increase ventilation during hypoxia only during the light phase. Conversely, CO2 promotes post-hypercarbic hyperpnea during both phases. We conclude that ORXs potentiate the post-hypercarbic (but not the hypoxic)-drive to breathe and are not involved in light/dark changes in the breathing pattern.

scholarly journals Melatonin MT1 and MT2 Receptors Exhibit Distinct Effects in the Modulation of Body Temperature across the Light/Dark Cycle

2019 ◽  
Vol 20 (10) ◽  
pp. 2452 ◽  
Author(s):  
Martha López-Canul ◽  
Seung Hyun Min ◽  
Luca Posa ◽  
Danilo De Gregorio ◽  
Annalida Bedini ◽  
...  
Keyword(s):  
Body Temperature ◽  
Receptor Antagonist ◽  
Partial Agonist ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Simultaneous Activation ◽  
Type 3 ◽  
G Protein Coupled

Melatonin (MLT) is a neurohormone that regulates many physiological functions including sleep, pain, thermoregulation, and circadian rhythms. MLT acts mainly through two G-protein-coupled receptors named MT1 and MT2, but also through an MLT type-3 receptor (MT3). However, the role of MLT receptor subtypes in thermoregulation is still unknown. We have thus investigated the effects of selective and non-selective MLT receptor agonists/antagonists on body temperature (Tb) in rats across the 12/12-h light–dark cycle. Rectal temperature was measured every 15 min from 4:00 a.m. to 9:30 a.m. and from 4:00 p.m. to 9:30 p.m., following subcutaneous injection of each compound at either 5:00 a.m. or 5:00 p.m. MLT (40 mg/kg) had no effect when injected at 5 a.m., whereas it decreased Tb during the light phase only when injected at 5:00 p.m. This effect was blocked by the selective MT2 receptor antagonist 4P-PDOT and the non-selective MT1/MT2 receptor antagonist, luzindole, but not by the α1/MT3 receptors antagonist prazosin. However, unlike MLT, neither the selective MT1 receptor partial agonist UCM871 (14 mg/kg) nor the selective MT2 partial agonist UCM924 (40 mg/kg) altered Tb during the light phase. In contrast, UCM871 injected at 5:00 p.m. increased Tb at the beginning of the dark phase, whereas UCM924 injected at 5:00 a.m. decreased Tb at the end of the dark phase. These effects were blocked by luzindole and 4P-PDOT, respectively. The MT3 receptor agonist GR135531 (10 mg/kg) did not affect Tb. These data suggest that the simultaneous activation of both MT1 and MT2 receptors is necessary to regulate Tb during the light phase, whereas in a complex but yet unknown manner, they regulate Tb differently during the dark phase. Overall, MT1 and MT2 receptors display complementary but also distinct roles in modulating circadian fluctuations of Tb.

Adrenal corticoids in hamsters: role in circadian timing

1985 ◽  
Vol 248 (4) ◽  
pp. R434-R438 ◽  
Author(s):  
H. E. Albers ◽  
L. Yogev ◽  
R. B. Todd ◽  
B. D. Goldman
Keyword(s):  
Wheel Running ◽  
Sampling Period ◽  
Dark Phase ◽  
Cortisol Secretion ◽  
Experimental Protocol ◽  
Light Phase ◽  
Dark Cycle ◽  
Physiological Control ◽  
Circadian Organization

The 24-h patterns of circulating cortisol and corticosterone were determined in male hamsters housed under a 14:10 light-dark cycle. Corticoid levels varied significantly over the 24-h sampling period with peak levels of both hormones occurring near the onset of the daily dark phase. The ratio of cortisol to corticosterone changed dramatically during the day. Corticosterone levels were significantly higher than cortisol during the early part of the light phase; however, cortisol levels became significantly higher than corticosterone when both hormones began their daily rise. To examine whether the circadian rhythm of cortisol secretion could be involved in the physiological control of hamster circadian organization, cortisol was infused at approximately physiological levels into adrenalectomized hamsters either continuously or in a 24-h rhythm. No significant differences were observed in the timing of circadian wheel-running rhythms in hamsters housed in LD 16:8, LD 14:10, or LL when cortisol was infused continuously, in a 24-h rhythm that mimicked the cortisol rhythm of intact hamsters, or in a 24-h rhythm several hours out of phase with the rhythm of intact hamsters. Provision of cortisol in a 24-h rhythm appeared to promote the survival of adrenalectomized hamsters since hamsters receiving a 24-h pattern of cortisol survived the experimental protocol significantly longer than those receiving the same dose of cortisol continuously.

scholarly journals Time matters: pathological effects of repeated psychosocial stress during the active, but not inactive, phase of male mice

2012 ◽  
Vol 215 (3) ◽  
pp. 425-437 ◽  
Author(s):  
Manuela S Bartlang ◽  
Inga D Neumann ◽  
David A Slattery ◽  
Nicole Uschold-Schmidt ◽  
Dominik Kraus ◽  
...  
Keyword(s):  
Social Preference ◽  
Active Phase ◽  
Time Of Day ◽  
Dark Phase ◽  
Light Phase ◽  
Immunological Parameters ◽  
Repeated Restraint Stress ◽  
Inactive Phase ◽  
Home Cage Activity

Recent findings in rats indicated that the physiological consequences of repeated restraint stress are dependent on the time of day of stressor exposure. To investigate whether this is also true for clinically more relevant psychosocial stressors and whether repeated stressor exposure during the light phase or dark phase is more detrimental for an organism, we exposed male C57BL/6 mice to social defeat (SD) across 19 days either in the light phase between Zeitgeber time (ZT)1 and ZT3 (SDL mice) or in the dark phase between ZT13 and ZT15 (SDD mice). While SDL mice showed a prolonged increase in adrenal weight and an attenuated adrenal responsiveness to ACTHin vitroafter stressor termination, SDD mice showed reduced dark phase home-cage activity on observation days 7, 14, and 20, flattening of the diurnal corticosterone rhythm, lack of social preference, and higherin vitroIFNγ secretion from mesenteric lymph node cells on day 20/21. Furthermore, the colitis-aggravating effect of SD was more pronounced in SDD than SDL mice following dextran sulfate sodium treatment. In conclusion, the present findings demonstrate that repeated SD effects on behavior, physiology, and immunology strongly depend on the time of day of stressor exposure. Whereas physiological parameters were more affected by SD during the light/inactive phase of mice, behavioral and immunological parameters were more affected by SD during the dark phase. Our results imply that repeated daily SD exposure has a more negative outcome when applied during the dark/active phase. By contrast, the minor physiological changes seen in SDL mice might represent beneficial adaptations preventing the formation of those maladaptive consequences.

Zur Analyse des Zeitsinnes bei Periplaneta americana

1959 ◽  
Vol 14 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Erwin Bünning
Keyword(s):  
Diurnal Cycle ◽  
Low Temperatures ◽  
Periplaneta Americana ◽  
Internal Clock ◽  
The Other ◽  
Dark Phase ◽  
Half Cycle ◽  
Light Phase ◽  
Dark Cycle ◽  
Running Activity

The running activity was used as a measure of the course of the endogenous diurnal periodicity in Periplaneta americana. The influence of low temperatures (+5°, +3°, -2°), which acted on the diurnal cycle at different times was tested. In one of the two half cycles the delay of the internal clock due to the chilling was smaller or equal to the duration of the chilling. During this phase, at least at temperatures greater than zero, a minimum time of chilling was necessary in order to demonstrate the delay clearly. In the other half cycle the delay is greater than the duration of the chilling.It is concluded that oscillations of relaxation are the basis of these phenomena. The phase of tension requires a minimum temperature. Below this minimum a gradual relaxation occurs. The phase of relaxation continues at low temperatures, but after some time it is gradually delayed.The normal 24-hour light-dark cycle regulates these oscillations in such a way that the phase of tension begins in the second half of the light phase and it attains its maximum in the first part of the dark phase.

scholarly journals Evidence for the role of hindbrain orexin-1 receptors in the control of meal size

2011 ◽  
Vol 301 (6) ◽  
pp. R1692-R1699 ◽  
Author(s):  
Eric M. Parise ◽  
Nicole Lilly ◽  
Kristen Kay ◽  
Amanda M. Dossat ◽  
Rohit Seth ◽  
...  
Keyword(s):  
Food Intake ◽  
Area Postrema ◽  
Dark Phase ◽  
Dark Cycle ◽  
Orexin A ◽  
Increase Food Intake ◽  
Double Label ◽  
Increased Activity ◽  
4Th Ventricle

Hypothalamic orexin neurons project to the hindbrain, and 4th-ventricle intracerebroventricular (4th-icv) injection of orexin-A treatment increases food intake. We assessed the effects of hindbrain orexin-A and the orexin-1-receptor antagonist SB334867 on meal pattern in rats consuming standard chow. When injected 4th-icv shortly before dark onset, lower doses of orexin-A increased food intake over a 2-h period by increasing the size of the first meal relative to vehicle, whereas the highest dose increased food intake by causing the second meal to be taken sooner. Conversely, hindbrain SB334867 reduced food intake by decreasing the size of the first meal of the dark phase. We also examined the effects of 4th-icv orexin-A and SB334867 on locomotor activity. Only the highest dose of orexin-A increased activity, and SB334867 had no effect. In addition, hindbrain SB334867 induced c-Fos in the nucleus of the solitary tract. These data support the suggestion that endogenous hindbrain orexin-A acts to limit satiation. Both orexin-A and the pancreatic satiation hormone amylin require an intact area postrema to affect food intake, so we asked whether 4th-icv orexin-A impairs the satiating effect of peripheral amylin treatment. Amylin reduced the size of the first meal of the dark cycle when rats were pretreated with 4th-icv saline, yet amylin was ineffective after 4th-icv orexin-A pretreatment. Using double-label immunohistochemistry, we determined that some orexin-A fibers in the area postrema are located in proximity to amylin-responsive neurons. Therefore, hindbrain orexin-A may increase food intake, in part, by reducing the ability of rats to respond to amylin during a meal.

Changes in body temperature of rats acclimated to heat with different acclimation schedules

1989 ◽  
Vol 67 (5) ◽  
pp. 2154-2157 ◽  
Author(s):  
O. Shido ◽  
Y. Yoneda ◽  
T. Nagasaka
Keyword(s):  
Wistar Rats ◽  
Heat Exposure ◽  
Heat Acclimation ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Hypothalamic Temperature ◽  
Male Wistar Rats ◽  
The Mean ◽  
Low Levels

Male Wistar rats, initially maintained at an ambient temperature (Ta) of 23.8 degrees C, were subjected to one of seven different heat acclimation schedules under a 12:12-h light-dark cycle (lights on at 0600 h). Two groups of rats were exposed to Ta of 32.4 degrees C all day for 5 (HC5) or 10 (HC10) days. The other four groups were exposed to Ta of 32.8 degrees C for 5 h/day during the last half of the dark phase for 5 (NI5) or 10 (NI10) consecutive days or during the last half of the light phase for 5 (DI5) or 10 (DI10) consecutive days. Control rats (C) were kept at 23.8 degrees C throughout the experiment. Hypothalamic temperature (Thy) was measured every 5 min with a chronically implanted thermocouple from 1 day before the beginning to 2 days after the end of the heat acclimation periods. During the heat acclimation periods, daily mean Thy rose significantly in HC5 and HC10 rats but decreased significantly in NI5 and NI10 rats. Daily mean Thy did not change in C, DI5, and DI10 rats. Thy in HC10 rats sharply decreased at the end of the heat acclimation periods and remained at low levels for approximately 3 h. On the 2nd postacclimation day, however, mean Thy returned and remained at a significantly higher level. In NI10 rats, the mean Thy in the postacclimation period was significantly lower than the preacclimation values. No such changes in mean Thy were observed in DI10 rats. Five-days of heat exposure had little effect on the postacclimation Thy.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Chronic oestrogen replacement in ovariectomised rats attenuates food intake and augments c-Fos expression in the suprachiasmatic nucleus specifically during the light phase

2011 ◽  
Vol 106 (8) ◽  
pp. 1283-1289 ◽  
Author(s):  
Akira Takamata ◽  
Kayo Torii ◽  
Kana Miyake ◽  
Keiko Morimoto
Keyword(s):  
Food Intake ◽  
Suprachiasmatic Nucleus ◽  
Female Rats ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Ovx Rats ◽  
Fos Expression ◽  
Insight Into ◽  
Ovariectomised Rats

Oestrogen replacement in ovariectomised (OVX) rats has been reported to attenuate food intake, especially during the light phase. To gain better insight into the central mechanism of oestrogen-induced reduction of food intake, we examined the effect of chronic oestrogen replacement in OVX rats on c-Fos expression in the suprachiasmatic nucleus (SCN) and on food intake during the light and dark phases. Eight-week-old female rats were ovariectomised and implanted with either an oestradiol (E2) or a vehicle pellet (Veh) subcutaneously. The animals were housed in an environment with a 12 h light–12 h dark cycle with the lights on at 07.00 hours. The amount of spontaneous food intake relative to each animal's body weight was significantly less for the E2 group than for the Veh group during the light phase, but there were no differences shown between these groups during the dark phase. There were no differences shown in the number of c-Fos-immunoreactive cells in the SCN in the E2 group compared with the Veh group during the early dark phase (22.00 hours; Zeitgeber time 15.00 (ZT15)), but the number was significantly higher than in the Veh group during the early light phase (10.00 hours; ZT3). This finding suggests that chronic oestrogen replacement chronically enhances SCN activity, specifically during the light phase. The oestrogen-induced enhancement of SCN activity during the light phase is possibly involved in the light phase-specific attenuation of food intake by oestrogen replacement in OVX rats.

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

2004 ◽  
Vol 287 (1) ◽  
pp. R174-R180 ◽  
Author(s):  
J. G. Ninomiya-Alarcón ◽  
R. Hudson ◽  
G. Reyes-Guerrero ◽  
B. Barrera-Mera ◽  
R. Guevara-Guzmán
Keyword(s):  
Mechanical Response ◽  
Contractile Response ◽  
Contractile Force ◽  
Dark Phase ◽  
Organ Bath ◽  
Light Phase ◽  
Dark Cycle ◽  
Pregnant Females ◽  
Pregnant Rabbit ◽  
Dose Dependent

We present findings suggesting that photoperiod is important in determining the sensitivity of the late-pregnant rabbit uterus to oxytocin (OT). Longitudinal myometrial strips were taken from term-pregnant and estrous rabbits and mounted in an organ bath for isometric myographic recording at different times during a 16:8-h light-dark cycle (lights on 0600–2200; n = 5/group), and the strength of contractions was registered in response to the application of OT or KCl. Strength of contractions was dose dependent and was up to 200 times greater at doses three to four orders of magnitude lower in tissue taken from pregnant animals during the light phase (0700 and 1300) than during the dark phase (2400 and 0400). Strips from nonpregnant estrous females also showed greater sensitivity and contractile force when taken in the light (0700) than in the dark (0400), although the differences were not significant. Consistent with the influence of photoperiod on uterine sensitivity to OT, strips taken from two groups of pregnant females ( n = 5/group) maintained on a light-dark cycle advanced 12 h showed significantly greater sensitivity and force in response to OT during the new subjective light than during the new subjective dark phase. The photoperiod-dependent contractile response to OT was specific and not simply the result of a change in general mechanical properties of the muscle, because administration of KCl resulted in dose-dependent contractions of similar magnitude in both the light and dark phase. These results are consistent with the fact that rabbits, like other nocturnal mammals, typically give birth during the day.

Diurnal variation of thermal resistance in rats

1980 ◽  
Vol 58 (10) ◽  
pp. 1174-1179 ◽  
Author(s):  
Y. Isobe ◽  
S. Takaba ◽  
K. Ohara
Keyword(s):  
Body Temperature ◽  
Heat Resistance ◽  
Time Of Day ◽  
Dark Phase ◽  
Diurnal Changes ◽  
Survival Times ◽  
Light Phase ◽  
Dark Cycle ◽  
Hot Environment ◽  
Normal Light

Effects of photoperiod on heat resistance were studied in 88 rats by observing their survival times in a hot environment (42.5 °C). Prior to the experiments individual rats were exposed to a given heat (42.5 °C) at a definite time of day and a "predicted survial time" in a given heat in individual rats was obtained. Rats were then divided into eight groups (with nine rats in each group) so as to ensure intergroup homogeneity regarding their predicted survival time and were exposed to heat at different times of day (every 3 h) until they were exhausted.It was found that the heat resistance varied with the time of day. In the eight groups kept under a normal light–dark cycle (L, 0700–1900; D, 1900–0700), heat resistances were observed to be significantly higher in the light phase than in the dark phase. Lethal body temperature was not correlated with the heat resistance. In two other groups (n = 8) kept under conditions reversed from the normal lighting cycle, resistance was higher in the nighttime (corresponding to the light phase when the rats were kept in the reversed lighting cycle) than in the morning (corresponding to the dark phase), these changes being accompanied by a phase shift of the diurnal changes in body temperature.

scholarly journals Effects of photoperiod on daily locomotor activity, energy expenditure, and feeding behavior in a seasonal mammal

2010 ◽  
Vol 298 (5) ◽  
pp. R1409-R1416 ◽  
Author(s):  
Amy Warner ◽  
Preeti H. Jethwa ◽  
Catherine A. Wyse ◽  
Helen I'Anson ◽  
John M. Brameld ◽  
...  
Keyword(s):  
Body Weight ◽  
Locomotor Activity ◽  
Energy Expenditure ◽  
Feeding Behavior ◽  
Heat Production ◽  
Prolonged Exposure ◽  
Dark Phase ◽  
Daily Rhythms ◽  
Dark Cycle ◽  
Activity Energy

The objective of this study was to determine whether the previously observed effects of photoperiod on body weight in Siberian hamsters were due to changes in the daily patterns of locomotor activity, energy expenditure, and/or feeding behavior. Adult males were monitored through a seasonal cycle using an automated comprehensive laboratory animal monitoring system (CLAMS). Exposure to a short-day photoperiod (SD; 8:16-h light-dark cycle) induced a significant decline in body weight, and oxygen consumption (V̇o2), carbon dioxide production (V̇co2), and heat production all decreased reaching a nadir by 16 wk of SD. Clear daily rhythms in locomotor activity, V̇o2, and V̇co2 were observed at the start of the study, but these all progressively diminished after prolonged exposure to SD. Rhythms in feeding behavior were also detected initially, reflecting an increase in meal frequency but not duration during the dark phase. This rhythm was lost by 8 wk of SD exposure such that food intake was relatively constant across dark and light phases. After 18 wk in SD, hamsters were transferred to a long-day photoperiod (LD; 16:8-h light-dark cycle), which induced significant weight gain. This was associated with an increase in energy intake within 2 wk, while V̇o2, V̇co2, and heat production all increased back to basal levels. Rhythmicity was reestablished within 4 wk of reexposure to long days. These results demonstrate that photoperiod impacts on body weight via complex changes in locomotor activity, energy expenditure, and feeding behavior, with a striking loss of daily rhythms during SD exposure.

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