Long-term exposures to higher environmental temperature and body temperature: effect of chlorpromazine in relation to hypothalamic GABA.

Treatment with a single dose of chlorpromazine (CPZ; 1 mg/kg, ip) at room temperature (28 degrees +/-0.5 degrees C) significantly reduced body temperature by its anticholinergic action. Long-term exposures to higher environmental temperature (40 degrees +/-0.5 degrees C, 2 h/day, for 30 consecutive days) increased body temperature significantly by reduction of hypothalamic GABAergic activity, but this increase in body temperature was attenuated from that observed with a single exposure to higher environmental temperature (40 degrees C for 2 h). Treatment with a single dose of CPZ on the last day of 30 consecutive days of exposures to higher environmental temperature increased body temperature of rats more than that observed with long-term exposures to higher environmental temperature possibly due to (i) reduction of hypothalamic GABAergic activity, (ii) heat dissipation and (iii) reverse-anticholinergic action of CPZ at higher environmental temperature.