Morphology of calretinin and tyrosine hydroxylase-immunoreactive neurons in the pig retina

The morphology of calretinin- and tyrosine hydroxylase-immunoreactive (IR) neurons in adult pig retina was studied. These neurons were identified usin g antibody immunocytochemistry, Calretinin immunoreactivity was found in nu merous cell bodies in the ganglion cell layer. Large ganglion cells, howeve r, were not labeled. In the inner nuclear layer, the regular distribution o f calretinin -IR neurons, the inner marginal location of their cell bodies in the inner nuclear layer, and the distinctive bilaminar morphologies of t heir dendritic arbors in the inner plexiform layer suggested that these cal retinin-IR cells were AII amacrine cells. Calretinin immunoreactivity was o bserved in both A-and B-type horizontal cells, Neurons in the photoreceptor cell layer were not labeled by this antibody. The great majority of tyrosi ne hydroxylase-IR neurons were located at the innermost border of the inner nuclear layer (conventional amacrines), The processes were monostratified and ran laterally within layer 1 of the inner plexiform layer, Some of the tyrosine hydroxylase- IR neurons were located in the ganglion cell layer (d isplaced amacrines), The processes of displaced tyrosine hydroxylase-IR ama crine cells were also located within layer 1 of the inner plexiform layer. Some processes of a few neurons were located in the outer plexiform layer, A very low density of neurons had additional bands of tyrosine hydroxylase- IR processes in the middle and deep layers of the inner plexiform layer. Th e processes of tyrosine hydroxylase-IR neurons extended radially over a wid e area and formed large, moderately branched dendritic fields. These proces ses occasionally had varicosities and formed "dendritic rings". These resul ts indicate that calretinin- and tyrosine hydroxylase-IR neurons represent specific neuronal cell types in the pig retina.