The neurons of the retinal ganglion cell layer of the guinea pig: quantitative analysis of their distribution and size.

1. The topographical distribution of ganglion cells and displaced amacrine cells in the guinea pig retina is described. 2. Neurons were counted in the ganglion cell layer of retinal whole mounts stained by the method of Nissl or retrogradely labeled with horseradish peroxidase. Neuronal soma size was estimated from samples taken from different retinal regions. 3. We estimate that a total of 295,000 neurons comprise the guinea pig ganglion cell layer and they consist of 159,000 ganglion cells and 136,000 displaced amacrine cells. 4. The visual streak is poorly differentiated. Ganglion cell density reaches a peak of 2,272 cells/mm2 in a temporal expansion of the visual streak, 4-5 mm toward the optic disk. The visual streak temporal expansion may represent the analogue of the area centralis for this species. The ventral hemi-retina has a higher ganglion cell density than the dorsal hemi-retina. The displaced amacrine cells are more uniformly distributed than the ganglion cells. 5. The present paper provides relevant data concerning the number and distribution of the neurons of the retinal ganglion cell which were not available or were very contradictory in the literature.