A light- and electron-microscopic study of goldfish corticotrops following lesions of the nucleus praeopticus.

The nucleus praeopticus (NPO) of the goldfish hypothalamus stimulates the secretion of adrenocorticotropic hormone (ACTH). Electrothermic lesions of the NPO significantly decreased stress-induced increments in plasma cortisol, but were without effect on plasma cortisol concentrations in undisturbed goldfish. Light microscopy and ultrastructural investigations of the corticotrops of goldfish bearing lesions of the NPO failed to reveal any differences in the status of morphological correlates usually associated with alterations in secretory activity. These observations demonstrate that hormones of the NPO-hypophyseal system stimulate ACTH release, but are not required for ACTH biosynthesis in goldfish corticotrops.