Abstract
Rat retina, which was intravitreously injected with 5-hydroxytryptamine (5-HT) or 5-hydroxytryp-tophane (5-HTP), was examined to identify indoleamine-accumulating cells by an immunohistochemical method in a flat-mount view and transverse sections. In the retina treated with 5-HT the immunostaining was observed in the cell processes, while in the retina treated with 5-HTP a large number of the immunoreactive cells with processes were noticeable. According to their morphological features and locations, they were divided into 5 types. Type 1 cells were large ovoid with a few processes and located in the inner lamina of the inner nuclear layer (INL). The majority of their processes ramified in the interface between the INL and inner plexiform layer (IPL). Type 2 and type 3 cells had large ovoid cell bodies, and the former was located in the ganglion cell layer (GCL) but the latter was placed in the IPL. Type 4 cells had small round cell bodies with a few fine processes and were placed in the inner lamina of the INL. Type 5 cells had the same features as type 4 cells but were displaced in the GCL.
These immunoreactive indoleamine-accumulating cells are categorized as amacrine cells from their shape and location. A morphological variety of indoleamine-accumulating cells in the rat retina indicates a wide range of involvement of amacrine cells in the signal transmission of visual information.
