IMMUNOCYTOCHEMICAL DEMONSTRATION OF NERVE GROWTH-FACTOR (NGF) RECEPTOR IN THE PINEAL-GLAND - EFFECT OF NGF ON PINEALOCYTE NEURITE FORMATION

Nerve growth factor receptor immunoreactivity (NGFRI) in the pineal gl and was examined both light and electron microscopically using the mon oclonal antibody 192IgG. NGFRI was located on sympathetic fibers and o n perivascular cells resembling macrophage/microglia. A pineal gland d ispersed cell culture model confirmed the presence of NGFRI in cells t hat exhibited processes of varying lengths and were distributed among pinealocytes and other flat cells. Pinealocytes in dispersed cell cult ure were identified immunocytochemically by their expression of S-anti gen, their round shape and small size and their tendency to extend neu rites in the direction of the flat cells in culture. The length of pin ealocyte neurites showed a significant increase when cultured in the p resence of NGF (25 ng/ml), suggesting that trophic factors, mediated b y these macrophage/microglial cells, are important to the morphogenesi s of these neuroendocrine cells. Neurotrophic activation of these neur oendocrine macrophage/microglia may have neuro-immunomodulatory implic ations leading to expression of proteins encoded by the major histocom patibility complex.