Endocrinology, Vol 129, 3125-3131, Copyright © 1991 by Endocrine Society

ARTICLES

Regulation of cholecystokinin octapeptide secretion by rat cerebral cortical cells in primary culture

J Abucham and S Reichlin
Department of Medicine, Tufts-New England Medical Center, Boston, Massachusetts 02111.

The regulation of cholecystokinin octapeptide (CCK-8) secretion was studied using a fetal cerebral cortical cell culture system. After 2-3 weeks in culture, the cells were utilized for short-term release experiments. CCK-8 was measured by RIA and its identity was confirmed by HPLC. Depolarization of the cells with K+ (6 x 10(-2) M) evoked CCK- 8 release and this response was blocked by the Ca++ channel blocker verapamil (2 x 10(-5) M) and by Ca++ free medium. The Na+ channel opener veratridine (10(-4) M) stimulated CCK-8 release and was blocked by the Na+ channel blocker tetrodotoxin (10(-6) M) and by Ca++ free medium. The adenylate cyclase activator forskolin (10(-5) M) markedly increased CCK-8 secretion. No changes in CCK-8 release were induced by epinephrine, norepinephrine, dopamine, acetylcholine, or 5- hydroxytryptamine at 10(-5) and 10(-4) M, but gamma-aminobutyric acid (GABA) at 10(-4) M inhibited CCK-8 release. GABA inhibition was reversed by the GABA antagonist picrotoxin (10(-4) M). Both picrotoxin (10(-4) M) and bicuculline (10(-3) M), another GABA receptor antagonist, alone stimulated CCK-8 secretion. These data show that CCK- 8 secretion by cerebral cortical cells 1) is stimulated by cell membrane depolarization in a calcium-dependent fashion, 2) is regulated by cAMP, 3) is unaffected by the neurotransmitters characteristic of corticopetal systems, 4) is tonically inhibited by GABA.