Presence of strong glucocorticoid receptor immunoreactivity within hypothalamic and hypophyseal cells containing pro-opiomelanocortic peptides.

The presence of nuclear glucocorticoid receptor immunoreactivity (GR IR) was studied in the adrenocorticotropin (ACTH), beta-Endorphin (beta-END) and alpha-melanocyte stimulating hormone (alpha-MSH) IR neuronal populations of the rat hypothalamus and hypophysis using double immunolabelling techniques. All the nuclei of the ACTH/beta-END/alpha-MSH IR neurons of the arcuate and periarcuate nuclei were strongly GR IR in the 48 h colchicine treated animal, but very few alpha-MSH-like IR perikarya located in the dorsal and lateral hypothalamus displayed nuclear GR IR. GR IR was present in the ACTH/beta-END corticotrophs and absent in the intermediate lobe of the hypophysis. The data provide morphological evidence for a glucocorticoid action through a nuclear GR in the arcuate ACTH/beta-END/alpha-MSH IR neurons and the ACTH/beta-END corticotrophs, whereas the alpha-MSH-like IR neurons of the lateral hypothalamus and the melanotropes of the intermediate lobe may not be directly affected by glucocorticoids under normal conditions.