Effect of pituitary hormones on phosphodiesterase and adenylate cyclase activity in brain tissuein vitro

: Effects of seiwhale somatotropin (STH), its biologically active fragment 77--107, porcine corticotropin (ACTH) and seiwhale prolactin on phosphodiesterase and adenylate cyclase activity of glial cells and synaptosomes isolated from the rat brain cortex were investigated. As compared with control, ACTH increased phosphodiesterase activity of glial cells by 392%, of synaptosomes by 123%, while STH by 49 and 77%, respectively, somatotropin fragment by 455 and 74%, and prolactin by 30 and 37%, respectively. Adenylate cyclase activity was significantly changed only by ACTH and only in synaptosomes (a 50% decrease). STH, its fragment and prolactin virtually failed to alter adenylate cyclase activity. The data obtained indicate that some of pituitary hormones, primarily ACTH and STH, may play the role of neuromodulators in some brain structures by decreasing the cyclic AMP level, by activating phosphodiesterase (STH and ACTH) and inhibiting adenylate cyclase (ACTH in synaptosomes).