ENDOGENOUSLY RELEASED DOPA IS PROBABLY RELEVANT TO NICOTINE-INDUCED INCREASES IN LOCOMOTOR ACTIVITIES OF RATS

The relevance of endogenously released DOPA to the (+/-)-nicotine-induced increase in locomotor activities was explored in rats. This increase was dose (0. 1 - 1.0 mg/kg, s. c.)-dependent, stereoselective and mecamylamine (1.0 mg/kg, s.c.)-sensitive, but was not antagonized by L-dopa methyl ester (200 mug, i.v.t.), a competitive L-dopa antagonist. Then, by microdialysis, low doses of alpha-methyl-p-tyrosine (alpha-MPT, i.p.) at 1 - 10 mg/kg, were tested to find a dose that selectively inhibits the basal DOPA release in the striata: the release was consistently inhibited by 3 mg/kg without any tendency to inhibit the basal dopamine release. Pretreatment with this dose did inhibit the nicotine-induced increases in locomotor activities. This suggests that endogenously released DOPA is in part relevant to the nicotine-induced behavior in rats.