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 a nd tyrosine hydroxylase positive cell populations within the ventral m esencephalon in cats recovered from parkinson-like motor deficits resu lting from previous MPTP administration was studied. A second or third series of MPTP injections in recovered cats initially reinstated park inson-like motor deficits. All cats again recovered normalized motor f unction two to three weeks after MPTP administration. Neurochemical an alysis of striatal tissue showed no or only minor differences in dopam ine 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 c onditions for the majority of the regions studied. These results sugge st that the mechanisms responsible for motor recovery from MPTP intoxi cation in cats can be transiently disrupted by further exposure to MPT P and that cats do not develop a permanent parkinsonian syndrome from repeated MPTP exposure.