Selective inhibition of MAO-B through chronic low-dose (R)-deprenyl treatment in C57BL/6 mice has no effect on basal neostriatal dopamine levels

C, Thiffault, L, Lamarre-Theroux, R, Quirion, and J, Poirier (1997, Mob Rro in Res, 44: 238-244) recently reported that chronic treatment of young (12 week old) C57BL16 mice with (R)-deprenyl, a mechanism-based inactivator of monoamine oxidase B (MAO-B), leads to a more than fourfold increase in neos triatal dopamine levels. Such an effect could complicate the interpretation of results obtained from mechanistic studies designed to evaluate the puta tive neuroprotective effects of (R)-deprenyl in 1-methyl-4-phenyl-1,2,3,6-t etrahydropyridine (MPTP)-lesioned mice. In contrast to the results of Thiff ault ct at, we have found that neostriatal dopamine levels in mature (32 we ek old) C57BL16 mice were unaltered by chronic (R)-deprenyl treatment even though brain monoamine oxidase B activity was reduced by more than 80%. Neo striatal dopamine levels also were unaltered in both young and mature mice when the (R)-deprenyl treatment period was doubled compared to that reporte d by Thiffault et al. Consequently, studies on the putative neuroprotective properties of (R)-deprenyl in MPTP-lesioned mice are unlikely to be compli cated by the possibility that inhibition of MAO-B alone will lead to an inc rease in neostriatal dopamine levels. (C) 2001 Academic Press.