INVOLVEMENT OF THE CENTRAL CATECHOLAMINERGIC SYSTEM IN NICOTINE-INDUCED TAIL-TREMOR IN RATS

The effect of 6-hydroxydopamine on repeated nicotine-induced tail-trem or was investigated in rats. Tail-tremor induced by nicotine (0.5 mg/k g/day, subcutaneously) became more pronounced in intensity with daily administration for 9 days. Rats pretreated with 6-hydroxydopamine (250 mu g, intracerebroventricularly) showed almost the maximum degree of tail-tremor during the whole experimental period, However, in rats pre treated with 6-hydroxydopamine plus desipramine, enhancement of tail-t remor was slight in the beginning but increased with the daily nicotin e administration. Fourteen-day administration of nicotine did not resu lt in significant changes in noradrenaline and dopamine levels in the cortex, hypothalamus, striatum and nucleus accumbens. These results su ggest that nicotine-induced tail-tremor is associated with the superse nsitivity of postsynaptic catecholaminergic receptors in the central n ervous system, and that the noradrenergic system may be more important than the dopaminergic system in this phenomenon.