Cholecystokinin-induced hypothermia: possible involvement of serotoninergic mechanisms in the rat hypothalamus.

The thermal effects of rats which were pretreated with 5,7-dihydroxytryptamine to deplete hypothalamic 5-hydroxytryptamine (5-HT) or with a 5-HT receptor blocker to intrahypothalamic administration of cholecystokinin (CCK) were compared with those of control rats. The CCK-induced hypothermic response was attenuated by pretreatment of the rats with either hypothalamic 5-HT depletion or receptor blockade. The reduction in the CCK hypothermia in the treated rats was due to the reduction of metabolic and vasomotor response. The data indicate that CCK may act on a 5-HT pathway within the hypothalamus to induce its hypothermia by promoting a reduction in metabolic heat production and an enhancement in heat loss in rats.