MPTP and MPP+ target specific aminergic cell populations in larval zebrafish.

Larval zebrafish offers a good model to approach brain disease mechanisms, as structural abnormalities of their small brains can be correlated to quantifiable behavior. In this study, the structural alterations in one diencephalic dopaminergic nucleus induced by 1-methyl-4-phenylpyridinium (MPP+), a toxin inducing Parkinson's disease in humans, and those found in several neuronal groups after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the pretoxin, were associated with decreased swimming speed. Detailed cell counts of dopaminergic groups indicated a transient decline of tyrosine hydroxylase expressing neurons up to about 50% after MPTP. The MPTP effect was partly sensitive to monoamine oxidase inhibitor deprenyl. Detailed analysis of the developing catecholaminergic cell groups suggests that the cell groups emerged at their final positions and no obvious significant migration from the original positions was seen. One 5-HT neuron group was also affected by MPTP treatment, whereas other groups remained intact, suggesting that the effect is selective. New nomenclature for developing catecholaminergic cell groups corresponding to adult groups is introduced. The diencephalic cell population consisting of groups 5,6 and 11 was sensitive to both MPTP and MPP+ and in this respect resembles mammalian substantia nigra. The results suggest that MPTP and MPP+ induce a transient functional deficit and motility disorder in larval zebrafish.