SELECTIVE SUPPRESSION OF TYPE-B MONOAMINE-OXIDASE IMMUNOREACTIVITY INTHE RAPHE NUCLEI FOLLOWING MPTP ADMINISTRATION IN THE CAT

USING immunohistochemistry, we investigated in the cat the effects of MPTP, a Parkinsonian syndrome-inducing substance, on brain type B mono amine oxidase (MAO-B) which is responsible for the conversion of MPTP to its neurotoxic product(MPP(+)). Intraperitoneal administration of M PTP (5 mg kg(-1) daily for 5 days) caused a selective suppression of M AO-B in neurones of the raphe nuclei without affecting hypothalamic MA O-B. Since these effects were accompanied by loss of nigral dopaminerg ic cells but not of raphe cell bodies or 5-HT immunoreactivity, we sug gest that MPTP suppresses raphe MAO-B without destroying its presumed host serotoninergic neurones and that raphe MAO-B does not appear to b e crucial in the MPTP-induced nigral lesion. In addition, the MPTP-ind uced paradoxical sleep suppression might be related to this raphe MAO- B loss.