Postnatal development of sympathetic and sensory innervation of the rhesus monkey ovary

We have used immunofluorescence to study the postnatal development of the sympathetic and sensory innervation to the rhesus monkey (Macaca mulatta) ovary. Sympathetic nerves were identified as adrenergic by their content of tyrosine hydroxylase (TH)-like immunoreactivity and as peptidergic by the presence of neuropeptide Y (NPY). Fibers containing substance P (SP) or calcitonin gene-related peptide (CGRP)-like immunoreactivity were considered as sensory, whereas vasoactive intestinal peptide (VIP)-positive fibers were only defined as peptidergic because VIP may be present in both sympathetic and sensory nerves. Ovaries from neonatal (2-mo-old), juvenile (9-18-mo-old), peripubertal (3-3.5-yr-old), adult (9-14-yr-old), and senescent (20-27-yr- old) monkeys were studied. At all ages, with the exception of senescence, TH- , NPY-, and VIP-containing fibers were associated with follicles in different developmental stages. In peripubertal and adult animals, some primordial follicles were found to be selectively innervated by VIPergic fibers that almost completely encircled each follicle. Both sympathetic and VIP fibers were also detected in the interstitial tissue and associated with the ovarian vasculature at all ages. The number of sympathetic and VIP fibers increased significantly (p < 0.01) between 2 mo and 9-18 mo of age, and again increased (p < 0.01) around the age of puberty (~3 yr of age). After this time, the number of NPY and TH fibers remained constant. Conversely, the number of VIP fibers decreased (p < 0.05) by 9-14 yr of age, but remained constant thereafter. The majority of fibers present were those containing NPY and TH, with VIPergic nerves being the least abundant. In contrast to the sympathetic and VIP innervation, sensory nerves containing SP were not detected, and those containing CGRP were scarce. While these had a localization similar to sympathetic nerve fibers, they were much less abundant and their number did not vary with age. The increase in density of sympathetic and VIPergic innervation that occurs before puberty and the striking relationship of VIP fibers to a minority of follicles in early stages of development suggest the possibility that sympathetic and VIP nerves may play a role in the process of follicular recruitment and maturation that leads to ovulation of a selected follicle. In addition, the absence of follicular innervation in senescent ovaries suggests that the decline in ovarian function during aging is associated with loss of neural inputs to the endocrine component of the gland.