Neuronal elements in the testis of the rhesus monkey: Ontogeny, characterization and relationship to testicular cells

Intrinsic neuron-like cells expressing the catecholamine-biosynthetic enzym e tyrosine hydroxylase (TH) were recently identified in the testis of the p repubertal rhesus monkey. In this study, we characterized the neuron-like n ature of these cells and examined distribution and frequency of neuronal el ements in the testes of monkeys during postnatal development, puberty and a dulthood. Using immunohistochemical methods, we detected both nerve fibers and cell bodies, immunoreactive for the neuronal markers neurofilament 200 (NF-200) and synaptosomal associated protein of 25 kDa (SNAP-25), TH and ne uropeptide Y (NPY) in perivascular locations, intermingled with interstitia l cells and close to the wall of seminiferous tubules. Marked age-related d ifferences in the numbers of these neuronal elements became apparent, when we quantified NF-200-immunoreactive neuronal elements. Thus, intrinsic neur on-like cell bodies were found only in the testes from immature animals (i. e., until about 3 years of age). Conversely, nerve fibers, presumably repre senting mainly the extrinsic innervation, were observed at all ages althoug h they became more prominent after the pubertal increase in LH and testoste rone levels. Interestingly, another testicular cell type known to contain p otent regulatory substances, mast cells, was found to be in close anatomica l proximity to nerve fibers. The number of these cells, positively identifi ed with an antibody to tryptase, increased significantly after puberty foll owing the same pattern as nerve fibers. These results confirm that the test icular nervous system of the monkey is composed of two components, intrinsi c nerve cells and extrinsic fibers, both of which are catecholaminergic and peptidergic in nature. Furthermore, both components show a marked degree o f plasticity during development, especially around the time of puberty. The intratesticular locations of neuronlike cells and fibers suggest that cate cholamines and neuropeptides are likely to have multiple sites of actions, and may affect Leydig cells, cells of the tubular wall and vascular cells d irectly and/or indirectly via intermediation of mast cells. Copyright (C) 2 000 S. Karger AG, Basel.