Amacrine and ganglion cells with corticotropin-releasing-factor-like immunoreactivity in the turtle retina.

This study, which uses immunocytochemical methods at the light microscopical, level, examines the cell types in the turtle retina that contain corticotropin-releasing factor (CRF)-like immunoreactivity. Two anatomically distinct amacrine cell types are labeled when antiserum directed against ovine CRF is used to label the turtle retina. These cell types each have a different dendritic arborization pattern and regional distribution. Type A cells are found only in the visual streak and have elongated dendritic arborizations that run parallel to the visual streak. These cells arborize primarily in stratum 1 and near the border of strata 2 and 3, with some processes extending into stratum 5. Type B amacrine cells are found only ventral to the visual streak and arborize primarily in a wide band in strata 4 and 5 with sparse dendritic arborizations in stratum 1. No labeled amacrine cells of any type were found dorsal to the visual streak. The asymmetric dendritic arborizations of the type A amacrine cells and the different regional distributions of the A and B cell types suggest that these two amacrine cell types perform distinct physiological functions. In addition to these labeled amacrine cells, there are also some immunoreactive cell bodies in the ganglion cell layer. Rhodamine crystals were applied to the optic tectum to retrogradely label the ganglion cell bodies. Double label studies indicate that some of the rhodamine-labeled ganglion cells also contain CRF-like immunoreactivity. The localization of CRF-like immunoreactivity in two distinct amacrine cell types and in ganglion cells suggests that it may play multiple roles in visual processing in the turtle retina.