Interaction effects of d-amphetamine treatment and ambient temperature on rat's food intake.

The "thermoregulatory theory of hunger" posits that rats placed in a cold environment should increase the amount of food intake, while rats placed in a hot environment should decrease their food intake. d-Amphetamine causes hyperthermia among rats kept at warm ambient temperature, and results in hypothermia among animals kept in a cold environment. d-Amphetamine-caused-hyperthermia should therefore result in decreased eating behavior, and d-amphetamine-caused hypothermia should result in increased eating behavior. One must take into account the fact that d-amphetamine is an anorexic drug. The interaction between (a) ambient temperature, (b) body temperature and (c) food intake were tested on groups of rats injected with various doses of d-amphetamine (1.5-15 mg/kg) and placed in ambient temperatures ranging from 4-37 degrees C. No increase in food intake was revealed under any dosage or temperature condition. The decrease in food intake found with d-amphetamine treated animals could not be explained in the "thermoregulatory theory of hunger". Our data indicate that d-amphetamine anorexic effects and thermal effects are mediated by different mechanisms.