Galanin inhibits ACTH release in vitro and can be demonstrated immunocytochemically in dispersed corticotrophs.

Double labeling of dispersed anterior pituitary cells revealed the coexistence of galanin immunoreactivity with adrenocorticotropic hormone (ACTH) as well as prolactin. However, only laser confocal microscopy showed three different areas of immunoreactivity within the corticotroph cytoplasm, two of them for ACTH and galanin separately and the third containing both immunoreactivities. To determine a possible relation between ACTH cells and galanin, 4-day cultures of anterior pituitary cells from female rats were examined by cell blot assay, and they showed ACTH release inhibition by 10(-6)M galanin. Furthermore, after 17 beta-estradiol treatment to maximize lactotroph galanin release in vitro, the cell blotting-assessed secretory level of corticotroph cells was very similar to that of cells in the presence of 10(-6)M galanin. In fact, immunoneutralization with galanin antiserum quenched the inhibitory effect of galanin on ACTH secretion. Our study suggests that locally produced galanin can modulate corticotropin release.