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 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.

Transient circadian internal desynchronization after light-dark phase shift in monkeys

1977 ◽  
Vol 232 (1) ◽  
pp. R31-R37 ◽  
Author(s):  
M. C. Moore-Ede ◽  
D. A. Kass ◽  
J. A. Herd
Keyword(s):  
Body Temperature ◽  
Saimiri Sciureus ◽  
Cycle Phase ◽  
Dark Phase ◽  
Dark Cycle ◽  
Water Excretion ◽  
Urinary Potassium ◽  
Timing System ◽  
Internal Desynchronization ◽  
Circadian Timing System

In four conscious chair-acclimatized squirrel monkeys (Saimiri sciureus) studied with lights on (600 lx) from 0800 to 2000 h daily (LD 12:12), prominent 24-h rhythms in feeding, drinking, activity, body temperature, and urinary potassium, sodium, and water excretion were seen. When the monkeys were subjected to 36 h of darkness followed by 36 h of light each variable demonstrated a circadian rhythm which was not passively dependent on the light-dark cycle. After the 24-h light-dark cycle was abruptly phase-delayed by 8 h, all the rhythms resynchronized with the new light-dark cycle phase, demonstrating that light-dark cycles are an effective zeitgeber. However, the resynchronization of the rhythms of feeding, drinking, activity, and body temperature was 90% complete within approximately 2 days while the 90% resynchronization of the urinary rhythms took approximately 5 days. These results suggest that the circadian timing system in S. sciureus may consist of several spontaneously oscillating units which can become transiently uncoupled during pertubations of environmental time cues.

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.

Shivering and digestion-related thermogenesis in pigeons during dark phase

1999 ◽  
Vol 277 (6) ◽  
pp. R1579-R1587 ◽  
Author(s):  
Michael E. Rashotte ◽  
Seppo Saarela ◽  
Ross P. Henderson ◽  
Esa Hohtola
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Dark Phase ◽  
Restricted Feeding ◽  
Light Phase ◽  
Feeding Experiments ◽  
Food Load ◽  
Kinetics Of ◽  
Maintain Body Temperature ◽  
Shivering Thermogenesis

The pigeon's main source of regulated heat production, shivering, is especially likely to be used for thermoregulation during the dark phase of the day when there is little heat from locomotor activity. However, food stored in the pigeon's crop is digested during the night, and digestion-related thermogenesis (DRT) will provide heat that should decrease the need for shivering to maintain body temperature (Tb). We investigated the conditions under which DRT alters the occurrence of nocturnal shivering thermogenesis in pigeons. In fasting experiments, in which DRT was minimal, variations in pectoral shivering were closely related to the kinetics of nocturnal Tb when the ambient temperature (Ta) was moderate (21°C). In that case, shivering was low while Tb fell at the beginning of the night, moderate during the nocturnal plateau in Tb, and strong during the prelight increase in Tb. Similar kinetics of nocturnal Tb occurred when Ta = 28°C, but shivering was negligible throughout the dark phase. In restricted feeding experiments, nocturnal DRT was varied by providing different amounts of food late in the light phase. When Ta = 21°C, 11°C, and 1°C, nocturnal Tb and O2 consumption were directly related to the amount of food ingested. However, nocturnal shivering tended to decrease as the food load increased and was significantly reduced at the higher loads. Because nocturnal shivering did not become more efficient in producing heat as the size of the food load increased, we conclude that nocturnal DRT decreased the need for shivering thermogenesis.

Diurnal Differences in the Innermost Surface of the S2 Layer in Differentiating Tracheids of Cryptomeria japonica Corresponding to a Light-Dark Cycle

Holzforschung ◽  
2003 ◽  
Vol 57 (6) ◽  
pp. 567-573 ◽  
Author(s):  
Y. Hosoo ◽  
M. Yoshida ◽  
T. Imai ◽  
T. Okuyama
Keyword(s):  
Cryptomeria Japonica ◽  
Dark Period ◽  
Amorphous Material ◽  
Light Period ◽  
Cellulose Microfibrils ◽  
Dark Phase ◽  
Diurnal Changes ◽  
Dark Cycle ◽  
Tangential Strain ◽  
S2 Layer

Summary This paper describes the effect of light on the diurnal change in the innermost surface of developing secondary walls. Cryptomeria japonica D. Don saplings were grown in two growth chambers, in which temperature and relative humidity were kept constant and the light-dark phase of the photoperiod varied. One chamber reproduced the natural light-dark phase, while the other reversed it. Samples of differentiating xylem were collected during the dark period when the tangential strain, used as an index of volumetric changes in differentiating cells, was high, and during the light period when the tangential strain was low. The innermost surface of developing secondary walls in differentiating tracheids was observed by field emission scanning electron microscopy. In the specimens collected during the dark period, amorphous material was observed and the cell wall surface was immunogold-labeled with an anti-glucomannan antiserum. In the specimens collected during the light period, cellulose microfibrils were clearly evident, and amorphous material and immunogold labeling were rarely observed. These results demonstrate that the diurnal changes in the innermost surface of developing secondary walls correspond to the light-dark cycle over 24 h.

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.

DIURNAL FLUCTATION OF PLASMA CORTISOL LEVELS IN THE GUINEA PIG

1979 ◽  
Vol 90 (4) ◽  
pp. 692-695 ◽  
Author(s):  
David R. Garris
Keyword(s):  
Guinea Pig ◽  
Cortisol Level ◽  
Plasma Cortisol ◽  
Plasma Cortisol Level ◽  
Dark Phase ◽  
Diurnal Changes ◽  
Light Phase ◽  
Dramatic Rise ◽  
Cortisol Levels

ABSTRACT Diurnal changes in the basal levels of plasma cortisol were studied in the female guinea pig. Plasma cortisol levels were determined at 8 bleeding times during the entrained 24 h photoperiod (14 h light/10 h dark: lights on 06.00 h). Plasma cortisol levels remained low during the dark phase of the cycle ranging between 6.4 and 9.0 μg/100 ml. However, at 4 h prior to the onset of the light phase of the photoperiod, a dramatic rise in the plasma cortisol level was measured, which peaked between 04.00 and 08.00 h at 12.3 μg/100 ml. A subsequent decline in plasma cortisol levels was measured throughout the light phase of the cycle, reaching basal levels before the onset of the dark phase. These data indicate that a diurnal fluctation in plasma cortisol occurs in the guinea pig which is very reminiscent of that seen in the human and in contrast with that observed in the rat.

The circadian component of spinule dynamics in teleost retinal horizontal cells is dependent on the dopaminergic system

1992 ◽  
Vol 9 (3-4) ◽  
pp. 345-351 ◽  
Author(s):  
H.-J. Wagner ◽  
U. D. Behrens ◽  
M. Zaunreiter ◽  
R. H. Douglas
Keyword(s):  
Dopaminergic System ◽  
Horizontal Cells ◽  
The Other ◽  
Control Fish ◽  
Control Group ◽  
Constant Darkness ◽  
Light Phase ◽  
Dark Cycle ◽  
Normal Light ◽  
Constant Dark

AbstractDuring the light phase of a light/dark cycle, dendrites of teleost cone horizontal cells display numerous finger-like projections, called spinules, which are formed at dawn and degraded at dusk, and are thought to be involved in chromatic feedback processes. We have studied the oscillations of these spinules during a normal light/dark cycle and during 48 h of constant darkness in two groups of strongly rhythmic, diurnal fish, Aequidens pulcher. In one group the retinal dopaminergic system had been destroyed by the application of 6-OHDA, while in the other (control) group, the dopaminergic system was intact. In control fish, oscillations of spinule numbers were observed under both normal and constant dark conditions, indicating the presence of a robust circadian rhythm. However, spinule dynamics were severely affected by the absence of retinal dopamine. During the normal light phase, the number of spinules in 6-OHDA injected retinae was strongly reduced, and throughout continual darkness, spinule formation was almost completely suppressed. These results indicate that dopamine is essential for both light-evoked and circadian spinule formation; furthermore, we conclude that there is no circadian oscillator within horizontal cells controlling the formation of spinules.

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.

Sign in / Sign up

Export Citation Format

Share Document