NICOTINE-INDUCED HYPOTHERMIA THROUGH AN INDIRECT DOPAMINERGIC MECHANISM

The effect of nicotine on core body temperature was studied in mice. I ntraperitoneal (i.p.) injection of nicotine (0.5, 1 and 2 mg/kg) induc ed a dose-dependent hypothermia. The response was inhibited by reserpi ne (5 mg/kg), the centrally active nicotinic receptor antagonist mecam ylamine (0.1-1 mg/kg) and the D-2 dopamine receptor antagonist sulpiri de (25-100 mg/kg). The beta-adrenoceptor antagonist propranolol (5 and 10 mg/kg) and the serotonergic blocker methysergide (5 and 10 mg/kg) did not inhibit but increased the nicotine response. The alpha-adrenoc eptor antagonist phenoxybenzamine, the antimuscarinic agent atropine, the D-1 dopamine receptor antagonist SCH 23390, the peripheral dopamin e antagonist domperidone and the peripheral nicotinic antagonist hexam ethonium did not alter the nicotine-induced hypothermia. It is conclud ed that nicotine may cause a fall in core body temperature through a c entral dopaminergic mechanism.