The amphetamine-like reinforcing effect and mechanism of L-deprenyl on conditioned place preference in mice

The present study investigated the reinforcing effect of L-deprenyl on conditioned place preference in mice and its mechanism. Conditioned place preference was induced by 10 and 25 mg/kg L-deprenyl in a dose-dependent fashion during five consecutive conditioning days, and its reinforcing property was about five-fold less potent than that of L-amphetamine. Pretreatment with the dopamine antagonist, haloperidol (1 mg/kg i.p.), effectively blocked the place preference produced by L-deprenyl (10 and 25 mg/kg i.p.) and L-amphetamine (2 and 5 mg/kg i.p.), but haloperidol itself produced no place aversion. The neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 30 mg/kg did not modify the place preference induced by both L-deprenyl and L-amphetamine, though the dopamine concentration in striata assayed by high performance liquid chromatography with electrochemical detection (HPLC-EC) was significantly reduced. These results suggest that L-deprenyl has amphetamine-like reinforcing properties. The reinforcing effect of L-deprenyl may be mediated by central dopaminergic neuronal systems, while the nigrostriatal dopaminergic pathway is not involved. (C) 1999 Elsevier Science B.V. All rights reserved.