IMMUNOHISTOCHEMICAL LOCALIZATION OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE (PACAP) IN THE ADRENAL-MEDULLA OF THE RAT

Localization of PACAP in rat adrenal glands was examined by light and electron microscopic immunohistochemistry using a specific antiserum t o PACAP 38, R0831. In the light microscopic study, PACAP immunoreactiv ity was observed in some cell groups in the medulla, but not in the co rtex. In comparison with adjacent sections stained with antisera to ca techolamine synthesizing enzymes, PACAP-positive cells were immunoreac tive to tyrosine hydroxylase and dopamine beta-hydroxylase, but not to phenylethanolamine-N-methyltransferase, suggesting that they were coi ncident with noradrenaline secreting cells. In the electron microscopi c study using the ABC method, DAB reaction products were diffusely dis tributed in the cytoplasmic matrix of PACAP-positive cells, without in tense accumulation on the secretory granules. The splanchnic nerve ter minals were PACAP negative. In postembedding immunohistochemistry, gol d particles were localized diffusely in the cytoplasma, but not aggreg ated on the secretory granules. It was suggested that PACAP would loca lize in the cytoplasmic matrix of noradrenaline cells and stimulate th e catecholamine synthesis and release in the adrenal medulla.