Immunohistochemical evidence for phenylethanolamine-N-methyltransferase-positive/tyrosine hydroxylase-negative neurones in the retina and the posterior hypothalamus of the rat.

Phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive neurons were observed in the inner nuclear layer of the rat retina, apparently giving rise to fiber networks mainly in layer 3 of the inner plexiform layer. These neurons did not seem to contain tyrosine hydroxylase (TH)-like or dopamine-beta-hydroxylase (DBH)-like immunoreactivity and were much smaller and more numerous than the previously described TH-positive dopamine neurons. PNMT-positive, but TH- and DBH-negative neurons were also observed in small numbers in the basal posterior hypothalamus.