EFFECTS OF NICOTINE ON METHYL-4-PHENYL-1,2,5,6-TETRAHYDROPYRIDINE-INDUCED DEPRESSION OF STRIATAL DOPAMINE CONTENT AND SPONTANEOUS LOCOMOTOR-ACTIVITY IN C57 BLACK MICE

The present study examined the effects of nicotine on the levels of do pamine and its metabolite 3,4-dihydroxy-phenylacetic acid (DOPAC) in t he striatum and on spontaneous locomotor activity of C57 black mice th at had been treated with the neurotoxin l-methyl-4-phenyl-1,2,5,6-tetr ahydropyridine (MPTP). The levels of dopamine and DOPAC in the striatu m were significantly reduced 10 days after two injections of MPTP (40 mg kg(-1), i.p., 24 h apart) in mice. Chronic treatment of nicotine (2 .0 mg kg(-1), s.c., four injections per day) did not influence the str iatal content of dopamine and DOPAC, but it significantly antagonised MPTP-induced depression of dopamine. However, the chronic nicotine tre atment did not significantly affect MPTP-induced depression of DOPAC. It was demonstrated that the lethal effect of MPTP was also partly pro tected by the chronic nicotine treatment. The chronic nicotine treatme nt also significantly protected MPTP-depressed spontaneous locomotor a ctivity in mice. The results suggest that both MPTP-depressed behaviou r and MPTP-induced striatal dopamine depletion in C57 black mice are p artly protected by chronic nicotine treatment. (C) 1998 The Italian Ph armacological Society.