Chronic chlorpromazine administration in rats: effects on ability to work in the heat

To identify and quantitate the effects of chronic chlorpromazine (CPZ) administration on the ability to work in the heat, 2 mg CPZ were administered by intraperitoneal injection daily for 14 days to rats weighing between 250 and 350 g at the time of experimentation. When these animals exercised in the heat (35 degrees C) to hyperthermic exhaustion (Tre = 42.5-43 degrees C), it was demonstrated that their endurance capacity was significantly reduced (P less than 0.001) when compared with saline-treated controls. Increments in rectal temperature while on the treadmill were significantly (P less than 0.02) elevated among th CPZ-treated rats. Exercise on the treadmill to hyperthermic exhaustion resulted in significantly (P less than 0.001) increased circulating levels of lactate and potassium when these were compared in blood samples taken immediately before and after exercise in the heat for both groups, but creatine phosphokinase levels were unaffected. Additionally, lactate levels were significantly (P less than 0.05) increased in the postrun blood samples of CPZ-treated rats when compared with the appropriate saline-treated controls. We concluded from these studies that chronic administration of CPZ in rats reduces their ability to work in the heat. Further, their rate of heat gain while exercising in the heat is increased, and the combined effects of exercise in the heat and CPZ administration exacerbated the effects on the clinical chemical indices of heat-exercise injury.