Effects of intracerebroventricular injection of d-amphetamine on metabolic, respiratory, and vasomotor activities and body temperatures in the rat.

Systemic and central administration of d-amphetamine both produced dose-dependent hypothermia in the rat at ambient temperature (Ta) 8 degrees C. The hypothermia was brought about solely by a decrease in metabolic heat production. However, at both Ta 22 and 30 degrees C, d-amphetamine produced hyperthermia accompanied by behavioral excitation. The hyperthermia was due to cutaneous vasoconstriction and increased metabolic heat production (due to behavioral excitation) at Ta 22 degrees C, whereas at Ta 30 degrees C the hyperthermia was due to cutaneous vasoconstriction, decreased respiratory evaporative heat loss, and increased metabolism (due to behavioral excitation). Furthermore, both the thermal and the behavioral responses induced by d-amphetamine were antagonized by pretreatment with intracerebroventricular administration of 6-hydroxydopamine (a depletor of central catecholaminergic nerve fibers). The data indicate that, by eliminating the interference of behavioral responses induced, d-amphetamine leads to an alteration in body temperature of rats by decreasing both metabolic heat production and sensible heat loss, probably via the activation of central catecholaminergic receptors.