IMMUNOHISTOCHEMICAL LOCALIZATION OF NEUROPEPTIDE-Y AND SOMATOSTATIN IN HUMAN FETAL RETINA

The localization of neuropeptide Y and somatostatin in the retina of six prenatal human specimens was determined by the utilization of light microscopic immunoperoxidase and immunefluorescence methods. The age of the prenatal fetuses ranged from 15 to 40 weeks of gestation. At 15 weeks, round or pear-shaped neuropeptide Y-immunopositive cells were observed in the inner nuclear layer and somatostatin immunoreactivity was only detected in the ganglion cell layer. Positive neuropeptide Y ganglion cells were observed by 17 weeks of gestation and by 28 weeks neuropeptide Y-immunopositive cells were demonstrated in the ganglion cell layer and inner nuclear layer. At 26-28 weeks, neuropeptide Y-immunopositive cells exhibited approximately the same shape as at 15 weeks of gestation, but the appearance of one or two processes was detected extending from the somata. By 38-40 weeks of gestation, neuropeptide Y-immunopositive cells were detected in the ganglion cell layer, inner nuclear layer and an immunopositive fibrous configuration in the inner plexiform layer. During this same period (38-40 weeks), somatostatin-positive cells were located in the ganglion cell layer, inner nuclear layer and the inner segments layers. Due to the difficulty of obtaining fetal materials, the exact time of initiation in the expression of neuropeptide Y and somatostatin is presently hard to delineate; however, it is safe to state that the peptides appear early in development.