The effects of nicotine administration on 5-HT uptake and biosynthesis in rat brain.

The effects of acute and chronic nicotine administration and its withdrawal on the rates of uptake and formation of 5-HT and the uptake of L-tryptophan, by synaptosomes prepared from discrete brain regions, have been studied in the rat. Both the acute and chronic (40 days) administration of nicotine (0.4 mg/kg s.c.) caused a decrease in the rate of formation of 5-HT by hippocampal synaptosomes (P less than 0.05) while 24 h withdrawal of the drug from chronically treated rats resulted in a partial recovery of this effect. Chronic nicotine treatment also reduced the rate of L-tryptophan uptake by hippocampal synaptosomes (P less than 0.01) an effect which appeared to be the result of a reduction in the number of L-tryptophan carrier molecules in the synaptosomal membrane. This effect, which was not reversed by withdrawal of the drug for 24 h, was not seen in synaptosomes prepared from other regions of the rat brain.