Retinal synaptogenesis in the primate.

Morphologic observations on early retinal synaptogenesis of Macaca mulatta fetuses of known gestational ages are described. Attempt is made to correlate the first appearance of synoptic vesicles, lamellar material, and the establishment of presynaptic contacts in both the inner and outer plexiform layers and in both types of synapses developing in these zones. Possible origin of lamellar material and synoptic vesicles are postulated, based on morphologic evidence derived from electron micrographs. Attention was focussed on fetal gestational stages from the earliest appearance of the outer plexiform layer to past midterm in gestation, just prior to the development of outer segment discs. Synoptic connections occurred in both layers nearly simultaneously and before the appearance of outer segment discs. Cone synaptogenesis preceded that of rods.