Carbamate-induced performance and thermoregulatory decrements restored with diazepam and atropine

When rats (500 g, male) are exercised on a treadmill, pretreatment with the carbamate physostigmine reduces endurance capacity (run time, RT) and increases the rate of rise of core temperature (heating rate, HR). Because physostigmine is a potential nerve agent pretreatment drug, our objective was to determine whether pharmacological intervention could reverse these decrements in performance and thermoregulation. The following drugs were administered separately via tail vein: vehicle-control (C), atropine (200 micrograms.kg-1, A), diazepam (500 micrograms.kg-1, D), and physostigmine (200 micrograms.kg-1, PH). After drug administration, rats were run (11 m.min-1, 6 degrees elevation, Ta = 26 degrees C) to exhaustion. PH administration resulted in reduced RT (41 min PH vs. 53 min C, p less than 0.05) with greater HR (0.090 degrees C.min-1 PH vs. 0.057 degrees C.min-1 C, p less than 0.01) than control rats. However, when A and D were also given to PH treated rats, the RT and HR were restored to control levels. Further, A and D without PH improved RT and HR (82 min, 0.047 degrees C.min-1) over control levels. Serial administration of an anticholinergic, an anticonvulsant, and an anticholinesterase resulted in no significant change in performance from control levels.