Intrinsic neurons in the rat ovary: an immunohistochemical study

Previous studies have shown the presence of neuronal perikarya in the prima te ovary, but not in the ovary from Sprague-Dawley rats. We report here: th at while such intrinsic neurons are indeed absent in this strain of rats, t hey can be visualized in the ovary from Wistar rats. The neurons, identifie d by their morphology and by the expression of NeuN (a neuron-specific nucl ear protein), were detected at all postnatal intervals examined, from 14 h after birth to 50 days of age. While they were present ill the ovarian hilu m and medulla at all ages studied, neurons first appeared in the ovarian co rtex during the juvenile period (postnatal days 10-20). In all cases, the s ize of the neuronal soma increased significantly during prepubertal develop ment, reaching maximal values before puberty. Some neurons were catecholami nergic, as indicated by their content of immunoreactive tyrosine hydroxylas e (TH), the rate-limiting enzyme of catecholamine biosynthesis. Some showed neuropeptide Y (NPY) immunoreactivity. TH-positive neurons were seen eithe r in isolation or clustered in ganglion-like structures in both the ovarian cortex and medulla. These results indicate that ovarian neurons are not pr esent in all strains of rats, but when present, the chemical phenotype of s ome of them is of a sympathetic nature, similar to that described in primat es.