Glucocorticosteroid injection is a circadian zeitgeber in the laboratory rat
Intraperitoneal temperatures were monitored by radiotelemetry to observe the thermoregulatory rhythm of male laboratory rats (Rattus norvegicus albinus). Rats received single injections of dexamethasone (as dexamethasone sodium phosphate) during constant darkness (0.1 lx) with food freely available or no food available. No phase shifts occurred following saline injection or dexamethasone at 1 mg/kg body wt. Depending on the phase of injection relative to the circadian cycle, dexamethasone at 10 mg/kg caused thermoregulatory peaks to be either delayed or advanced on the 4th and 5th days after injection. There was an insensitive interval which corresponded to subjective day. Phase shifts induced by dexamethasone during ad libitum feeding were of less magnitude than those induced during starvation. The determination of phase-shifting parameters (i.e., a phase-response curve) for hormonal substances represents a rigorous and broadly applicable technique for determining endogenous mechanisms for circadian phase control and entrainment.
- Research Organization:
- Argonne National Lab., IL
- OSTI ID:
- 6419548
- Journal Information:
- Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 243:3; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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560205 -- Thermal Effects-- Vertebrates-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ADRENAL HORMONES
ANIMALS
BIOLOGICAL EFFECTS
COMMUNICATIONS
CONTROL
CORTICOSTEROIDS
DAILY VARIATIONS
DATA TRANSMISSION
DEXAMETHASONE
GLUCOCORTICOIDS
HORMONES
HYDROXY COMPOUNDS
KETONES
MAMMALS
ORGANIC COMPOUNDS
PREGNANES
RATS
RODENTS
STEROID HORMONES
STEROIDS
TELEMETRY
TEMPERATURE CONTROL
THERMOREGULATION
VARIATIONS
VERTEBRATES