Atropine, diazepam, and physostigmine: thermoregulatory effects in the heat-stressed rat.
We have previously reported that administration of atropine (A) to unrestrained, sedentary, heat-stressed rats resulted in a dose-dependent increase in heating rate (rate of rise of core temperature, degree C/min). Additionally, we have demonstrated that the decrements in treadmill endurance and increments in heating rate of physostigmine (PH)-treated running rats can both be restored to control levels by pretreating the animals with A and diazepam (D). Our objective in the present work was to determine if the administration of D + PH to A-treated unrestrained, sedentary, heat-stressed rats (N = 16/group, 510-530 g) could improve their thermal tolerance. The following drugs were administered singly (at 10 min intervals) via lateral tail vein: vehicle-control (C), A (200 micrograms/kg), D (500 micrograms/kg), and PH (200 micrograms/kg). After drug administration, the rats were heat-stressed (Tamb = 41.5 degrees C) until a core temperature of 42.6 degrees C was attained when they were removed to a 26 degrees C chamber. The heating rates (degrees C/min) and tolerance times (min) of the respective groups were: C- 0.02, 235; A- 0.08, 58; A D- 0.06, 94; and A + D + PH- 0.04, 143. Administration of D with A significantly decreased heating rate, and D + PH more than doubled the thermal tolerance of A-treated rats. Thus, the combination of A + D + PH not only restores PH-induced performance and thermoregulatory decrements of rats exercised in a moderate environment, but also reduces A-induced heat intolerance.
Matthew
C B
CB
US Army Research Institute of Environmental Medicine, Natick, MA 01760-5007.
Hubbard
R W
RW
Francesconi
R P
RP
D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D001833:Body Temperature Regulation / Q000187:drug effects*; D003975:Diazepam / Q000494:pharmacology*; D006358:Hot Temperature; D008297:Male; D005082:Physical Exertion; D010830:Physostigmine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012472:Salivation / Q000187:drug effects; D013312:Stress, Physiological / Q000503:physiopathology*
D001285:Atropine; D010830:Physostigmine; D003975:Diazepam