Effect of the glucocorticoid milieu on the immunostaining of peptide histidine isoleucine (PHI) in the rat hypothalamus

Effects of adrenalectomy (ADX) or dexamethasone (DEX) treatment on the immunostaining of hypothalamic peptide histidine isoleucine (PHI) were examined in male rats. After colchicine treatment, PHI-containing cell bodies were observed in the suprachiasmatic nucleus (SCN) and the parvocellular division of the paraventricular nucleus (PVN). ADX increased and DEX dose-dependently decreased the number of PHI-immunopositive neurons in the PVN. The number of SCN-PHI neurons was not affected by any treatment employed in this study. These results suggest that PVN-PHI neurons are under the effects of the glucocorticoid milieu, and that the neurons may be involved in the glucocorticoid regulation of adrenocorticotropin and prolactin secretion.