Effect of reserpine treatment and hypophysectomy on the nitric oxide synthase immunoreactivity and NADPH‐diaphorase staining in the rat adrenal gland

Background The presence of nitric‐oxide‐synthesising neurons in the adrenal gland has recently been described by the immunohistochemical and/or enzyme histochemical demonstration of its synthesising enzyme, nitric oxide synthase (NOS; Afework et al. 1994. Cell Tissue Res, 276: 133–141). In the present report, these neurons have been examined by studying the changes that occur during conditions known to affect the adrenal gland. Methods By using NOS immunohistochemistry and NADPH‐diaphorase histochemistry, levels of NOS and/or NADPH‐diaphorase containing cellular elements in the adrenal gland were studied in rats subjected to either reserpine treatment or hypophysectomy as compared with the controls. Results Reserpine treatment caused a significant decrease in immunoreactivity to the neuronal isoform of NOS in the nerve fibres that innervate adrenal medullary cells. Hypophysectomy did not cause any change in the NOS immunoreactivity, although it eliminated most of the NADPH‐diaphorase‐staining non‐NOS‐immunoreactive cortical cells. Conclusions The reduction in the level of NOS in the reserpine treated rats may indicate a decrease in the production of nitric oxide in the gland; this action may be related to the increase in the biosynthesis and secretion of catecholamine, which follows treatment with the drug. The reduction in the NADPH‐diaphorase‐positive cells may reflect the elimination of adrenal cortical cells that occurs after hypophysectomy, whereas hypophysectomy by itself appears to have no effect on the level of production of nitric oxide in the gland. © 1996 Wiley‐Liss, Inc.