Reversible effects of 1-methyl-4-phenylpyridinium ion (MPP(+)) on dopaminergic neurons in goldfish retina

The effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium ion (MPP(+)) on the dopamine (DA), norepinephrine (NA) and serotonin (5-HT) levels in goldfish retina, was investigated. Intravitreal (i.v.) injection of MPTP (10 ?g) caused a 60-70% depletion of DA, which was prevented by the simultaneous administration of pargyline (10 ?g). A similar dopamine depletion was observed with MPP(+) (10 ?g). In contrast, NA or 5-HT levels were unaffected by MPTP or MPP(+). Time-course studies revealed that MPP(+)-induced DA depletion in goldfish retina was almost completely reversed within 2 months. The results confirm the selective action of MPP(+) towards dopaminergic neurons in goldfish retina.