Do central mechanisms participate in the thermoregulatory activity of prazosin?

1. Prazosin (PRA) was used in febrile (LPS; 1 mcg/kg; i.v.) and normothermic rabbits at ambient temperatures (Ta) of 5, 19 and 28 degrees C. This drug was given i.v. in the form of an infusion at a rate of 0.75 mg/kg/3 hr. 2. In normothermic animals, PRA produced significant hypothermia mainly at Ta of 5 and 19 degrees C. In a cold environment, the hypothermic effect of PRA was associated with inhibition of metabolic rate and evaporative heat loss. 3. Infusion of this drug significantly prevented the LPS-induced fever in all experimental conditions. In the cold environment, a drop in body temperature was correlated with an inhibition of metabolic rate; in the thermoneutral environment, antipyresis was associated with an increase in heat dissipation from the ear-skin area; in the hot environment, the correlation between antipyresis and mechanisms of heat dissipation was much less clear. 4. The possible action of PRA on the effector part of the central thermoregulatory system is discussed.