Repeated exposure to MPTP does not produce a permanent movement disorder in cats recovered from MPTP-induced parkinsonism.

The effects of additional MPTP injections on striatal neurochemistry and tyrosine hydroxylase positive cell populations within the ventral mesencephalon in cats recovered from parkinson-like motor deficits resulting from previous MPTP administration was studied. A second or third series of MPTP injections in recovered cats initially reinstated parkinson-like motor deficits. All cats again recovered normalized motor function two to three weeks after MPTP administration. Neurochemical analysis of striatal tissue showed no or only minor differences in dopamine and metabolite levels within most striatal regions sampled between cats which received single or multiple sets of MPTP injections. Cell count results showed no significant differences between the two MPTP conditions for the majority of the regions studied. These results suggest that the mechanisms responsible for motor recovery from MPTP intoxication in cats can be transiently disrupted by further exposure to MPTP and that cats do not develop a permanent parkinsonian syndrome from repeated MPTP exposure.