Effects of sarin on temperature and activity of rats as a model for gulf war syndrome neuroregulatory functions.

Coexposure to subclinical levels of nerve gas and to heat stress may have induced some of the clinical symptoms of the Gulf War Syndrome. We tested the hypothesis that single or repeated subclinical exposure to sarin, particularly under conditions of heat stress, would impair regulation of body temperature and locomotor activity. Male F344 rats were housed at 25 degrees C or under mild heat stress at 32 degrees C and were exposed 1 h/day for 1, 5, or 10 days to 0, 0.2, or 0.4 mg/m(3) of sarin in a nose-only exposure system. Body temperature and activity were monitored continuously by telemetry during exposure and 1 month postexposure. Exposed rats showed no clinical symptoms of toxicity such as tremors, despite evidence of reduced red blood cell cholinesterase activity. Heat stress consistently elevated body temperature in unexposed animals, particularly during the dark period when animals are most active. Inhalation of sarin gas at the two subclinical levels did not affect body temperature acutely in a biologically meaningful manner after the first exposure nor after 5 or 10 repeated exposures, either at thermoneutral ambient temperature or during chronic heat stress. There were no consistent effects of sarin or housing temperature on activity. The data suggest that subclinical levels of sarin have minimal effects on temperature regulation and locomotor activity under these observation conditions.