SOMATOSTATIN-LIKE IMMUNOREACTIVE CELLS IN THE GROUND-SQUIRREL RETINA

Immunocytochemical techniques were employed to locate somatostatin (SS )-containing cells in the retina of the 13-lined ground squirrel (Sper mophilus tridecemlineatus). In normal retinas immunostain was limited to neuronal processes, yet distinctly labeled somata were detected in retinas of animals pretreated with colchicine. Labeled cell bodies wer e located in the outermost and innermost portions of the inner nuclear layer (INL) and in the ganglion cell layer (GCL). The largest populat ion of SS-like immunoreactive neurons was found in the innermost INL. These cells were identified as small and medium sized amacrine cells w hose soma diameters ranged from 4 to 14 mu m. A smaller population of immunoreactive cells was observed in the outermost region of the INL. These cells, presumptive horizontal cells, were found mainly in periph eral regions of the retina. Immunoreactive cells in the GCL were of tw o types: displaced amacrines, and retinal ganglion cells. SS-positive axons in the optic fiber layer suggest that some of the immunoreactive GCL neurons were ganglion cells, and it is our opinion that these cel ls belong to a class of associational ganglion cells previously identi fied in other-species. (C) 1997 Academic Press Limited.