Tyrosine hydroxylase immunohistochemistry in the normal and 1-methyl-4-phenyl-tetrahydropyridine (MPP+)-treated retina of goldfish

Dopaminergic interplexiform neurons have been identified in the inner nuclear layer of goldfish retina, with tyrosine hydroxylase (TH) immunocytochemistry in whole-mounted retinae and in cryosections. The neurotoxin 1-methyl-4-phenylpyridinium ion (MPP+), which selectively damages dopaminergic neurons in mammals, caused a marked depletion of TH immunoreactivity in goldfish retina. Three days after intravitreal injection, retinae showed no significant decrease in the number of TH-positive neurons. However most of the TH-immunoreactive cell bodies showed an evident depletion of TH immunoreactivity and their processes, ramified in the inner and outer plexiform layers, disappeared almost completely.