Bombesin-induced hypothermia: possible involvement of cholinergic and dopaminergic receptors in the rat hypothalamus.

The thermal responses of rats which were pretreated with 5,7-dihydroxytryptamine to deplete hypothalamic 5-hydroxytryptamine, 6-hydroxydopamine to deplete hypothalamic catecholamines, phentolamine and propranolol to inhibit adrenergic receptors, haloperidol to inhibit dopamine receptors, or atropine to inhibit cholinergic receptors, to intrahypothalamic administration of bombesin were compared with those of control rats. The bombesin-induced hypothermia was attenuated by pretreatment of the rats with either hypothalamic dopamine depletion or receptor blockade, or hypothalamic cholinergic receptor blockade. The reduction in the bombesin-induced hypothermia in the treated rats was due to the reduction of metabolic and vasomotor response. The data indicate that bombesin may act on hypothalamic dopamine and/or cholinergic receptor mechanisms to induce hypothermia by promoting a reduction in metabolic heat production and an enhancement in heat loss in rats.