Retinal dopaminergic neurons (A17) expressing neuromedin K receptor (NK(3)): a double immunocytochemical study in the rat.

By using a double immunofluorescence method we examined the distribution of dopaminergic neurons (A17) expressing neuromedin K receptor (NKR, NK(3)) in the rat retina. The distribution of NKR-like immunoreactive (-LI) neurons partially overlapped that of tyrosine hydroxylase (TH)-LI neurons in the inner retina of section and flat-mount preparation. Neurons showing both TH- and NKR-like immunoreactivities were found in the retina (A17): 100% of these TH-LI neurons displayed NKR-like immunoreactivity, and they constituted about 3.5% of total NKR-LI neurons. The majority of double-labeled neurons with TH- and NKR-like immunoreactivities were distributed in the proximal inner nuclear layer and the upper part of inner plexiform layer of the retina, and characterized with appearance of amacrine cells. The present study has provided morphological evidence for direct physiological modulation of dopaminergic neurons by tachykinins through NKR in the rat retina (A17).