Possible mechanisms involved in the hyperthermic effect caused by reserpine after pretreatment with amphetamine or tranylcypromine in conscious rat.

Reserpine injected intravenously induced a hyperthermic response in rats pretreated one hour before with amphetamine or tranylcypromine. Pretreatment of rats with alpha-methyl-p-tyrosine (alpha-MT) before the interaction of tranylcypromine-reserpine or amphetamine-reserpine, significantly blocked the potentiation of the increase in temperature that was seen after reserpine. Pretreatment with p-chloro-phenyl-alanine (PCPA) partially abolished the potentiation of the increase in temperature that was seen after reserpine. The dopamine receptor antagonists prevented the hyperthermia induced by the interaction of tranylcypromine-reserpine. However, they only partially inhibited the rise of body temperature induced by reserpine in rats pretreated with amphetamine. Methysergide, a serotoninergic receptor blocker, only reduced the hyperthermic effect in both instances. In conclusion, in the rat potentiation of the increase in temperature induced by tranylcypromine before reserpine would appear to involve a main dopaminergic component and a lesser but significant noradrenergic and serotoninergic component. However, in hyperthermia induced by the combination of amphetamine plus reserpine it is unknown which of these amines plays a predominant role in the development of hyperthermia.