Torpor shortens the period of Siberian hamster circadian rhythms

We investigated the influence of ambient and body temperature (Ta and Tb) on circadian rhythms of gonadectomized male Siberian hamsters. Animals that entered torpor (Tb < 30 degrees C) had significantly shorter circadian periods (tau s) than did nontorpid hamsters at a Ta of 13 degrees C (24.17 +/- 0.05 vs. 24.33 +/- 0.04 h). The tau s of homeothermic hamsters were not affected by Ta change. Short-term decreases in Tb, rather than changes in Ta, appear to affect tau. Access to activity wheels inhibited expression of torpor in short daylengths and was associated with significant increases in body mass. Running wheel activity can mask or block specific short-day responses.

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Effect of Continuous Light on the Circadian Rhythms of Running-Wheel Activity and Body Temperature in Spontaneously Hypertensive Rats

Medical Principles and Practice ◽

10.1159/000157352 ◽

1990 ◽

Vol 2 (3-4) ◽

pp. 138-147 ◽

Cited By ~ 3

Author(s):

Yoshiaki Isobe ◽

Kyuzo Aoki ◽

Fujiya Furuyama ◽

Takeshi Hashitani

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Spontaneously Hypertensive Rats ◽

Continuous Light ◽

Hypertensive Rats ◽

Running Wheel ◽

Spontaneously Hypertensive ◽

Wheel Activity

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Organization of rat circadian rhythms during daily infusion of melatonin or S20098, a melatonin agonist

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1999.277.3.r812 ◽

1999 ◽

Vol 277 (3) ◽

pp. R812-R828 ◽

Cited By ~ 14

Author(s):

B. Pitrosky ◽

R. Kirsch ◽

A. Malan ◽

E. Mocaer ◽

P. Pevet

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Phase Response Curve ◽

Constant Darkness ◽

Time Interval ◽

General Activity ◽

Activity Peak ◽

Free Running ◽

Wheel Activity ◽

Free Running Period

Daily administration of melatonin or S20098, a melatonin agonist, is known to entrain the free-running circadian rhythms of rats. The effects of the duration of administration on entrainment were studied. The animals demonstrated free-running circadian rhythms (running-wheel activity, body temperature, general activity) in constant darkness. Daily infusions of melatonin or S20098 for 1, 8, or 16 h entrained the circadian rhythms to 24 h. Two daily infusions of 1 h (separated by 8 h) entrained the activity peak within the shorter time interval. The entraining properties of melatonin and S20098 were similar and were affected neither by pinealectomy nor by infusion of 1- or 8-h duration. However, with 16-h infusion, less than half of the animals became entrained. Once entrained, the phase angle between the onset of infusion and the rhythms (onset of activity or acrophase of body temperature) increased with the duration of infusion. Before entrainment, the free-running period increased with the duration of infusion, an effect that was not predictable from the phase response curve.

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Hypoglycemia and torpor in Siberian hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1999.276.3.r776 ◽

1999 ◽

Vol 276 (3) ◽

pp. R776-R781 ◽

Cited By ~ 6

Author(s):

John Dark ◽

Daniel A. Lewis ◽

Irving Zucker

Keyword(s):

Blood Glucose ◽

Body Temperature ◽

Body Mass ◽

Air Temperature ◽

Day Length ◽

Siberian Hamsters ◽

Long Day ◽

Necessary And Sufficient ◽

Blood Glucose Concentrations ◽

Torpor Bouts

We tested whether reduced blood glucose concentrations are necessary and sufficient for initiation of torpor in Siberian hamsters. During spontaneous torpor bouts, body temperature (Tb) decreases from the euthermic value of 37 to <31°C. Among hamsters that displayed torpor during maintenance in a short-day length (10 h light/day) at an air temperature of 15°C, blood glucose concentrations decreased significantly by 28% as Tb fell from 37 to <31°C and increased during rewarming so that by the time Tb first was >36°C, glucose concentrations had returned to the value preceding torpor. Hamsters did not display torpor when maintained in a long-day length (16 h light/day) and injected with a range of insulin doses (1–50 U/kg body mass), some of which resulted in sustained, pronounced hypoglycemia. We conclude that changes in blood glucose concentrations may be a consequence rather than a cause of the torpid state and question whether induction of torpor by 2-deoxy-d-glucose is due to its general glucoprivic actions.

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Effects of anabolic androgenic steroids on the development and expression of running wheel activity and circadian rhythms in male rats

Physiology & Behavior ◽

10.1016/j.physbeh.2007.07.010 ◽

2007 ◽

Vol 92 (5) ◽

pp. 1010-1018 ◽

Cited By ~ 39

Author(s):

Marilyn Y. McGinnis ◽

Augustus R. Lumia ◽

Marc J. Tetel ◽

Heather A. Molenda-Figueira ◽

Bernard Possidente

Keyword(s):

Circadian Rhythms ◽

Male Rats ◽

Anabolic Androgenic Steroids ◽

Running Wheel ◽

Wheel Activity ◽

Androgenic Steroids

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Physical training intervention in female shift workers: II. The effects of intervention on the circadian rhythms of alertness, short-term memory, and body temperature

Ergonomics ◽

10.1080/00140138808966648 ◽

1988 ◽

Vol 31 (1) ◽

pp. 51-63 ◽

Cited By ~ 51

Author(s):

M. I. HÄRMÄ ◽

J. ILMARINEN ◽

P. KNAUTH ◽

J. RUTENFRANZ ◽

O. HÄNNINEN

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Physical Training ◽

Short Term Memory ◽

Training Intervention ◽

Short Term ◽

Shift Workers ◽

Term Memory

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Acute dim light at night increases body mass, alters metabolism, and shifts core body temperature circadian rhythms

Chronobiology International ◽

10.3109/07420528.2014.926911 ◽

2014 ◽

Vol 31 (8) ◽

pp. 917-925 ◽

Cited By ~ 33

Author(s):

Jeremy C. Borniger ◽

Santosh K. Maurya ◽

Muthu Periasamy ◽

Randy J. Nelson

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Body Mass ◽

Core Body Temperature ◽

Light At Night ◽

Dim Light ◽

And Shifts ◽

Core Body

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Melatonin attenuates photic disruption of circadian rhythms in Siberian hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.273.4.r1540 ◽

1997 ◽

Vol 273 (4) ◽

pp. R1540-R1549 ◽

Cited By ~ 3

Author(s):

Norman F. Ruby ◽

Tom Kang ◽

H. Craig Heller

Keyword(s):

Body Temperature ◽

Circadian Rhythms ◽

Phase Shift ◽

Adult Male ◽

Circadian System ◽

Light Phase ◽

Siberian Hamsters ◽

Free Running ◽

Hyperthermic Response ◽

Injection Regimen

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

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