Effects of exercise conditioning on thermoregulatory response to anticholinesterase insecticide toxicity

Chronic exercise conditioning has been shown to alter basal thermoregulatory processes (change in thermoregulatory set point) as well as the response to infectious fever Chlorpyrifos (CHP), an organophosphate insecticide, also affects thermoregulation, causing an acute period of hypothermia followed by a delayed fever. This study examined whether chronic exercise training in the rat alters the thermoregulatory response to CHP. Core temperature and motor activity were monitored by radiotelemetry in female Sprague-Dawley rats housed individually at an ambient temperature of 22 degrees C. The rats were either given continuous access to running wheels or housed in standard cages without wheels. The exercise group ran predominately at night. After 8 weeks, the rats were gavaged with corn oil or 15 mg/kg CHP. CHP induced a transient hypothermic response followed by a delayed fever, beginning 1 day after exposure. Relative to controls, T7 decreases were not significantly different between the exercise (1.6 degrees C) group and the sedentary (0.5 degrees C) group given CHP. The sedentary and exercise group administered CHP developed a fever the day after CHP treatment. The fever response was greater in the sedentary group and persisted for approximately 3 days post-injection. Fever of the exercise group persisted for just one-half of 1 day after CHP. It is well known that chronic exercise training improves aerobic capacity; however, trained rats were not protected from the hypothermic effects of CHP. Training did ameliorate the febrile effects of CHP. Thus, exercise training may afford protection to the toxic effects of organophosphate insecticides.