Regulation of cholecystokinin octapeptide secretion by rat cerebral cortical cells in primary culture.
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.
Department of Medicine, Tufts-New England Medical Center, Boston, Massachusetts 02111.
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Abucham
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Reichlin
D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004622:Embryo, Mammalian; D018756:GABA Antagonists; D008564:Membrane Potentials / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012844:Sincalide / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018756:GABA Antagonists; D018377:Neurotransmitter Agents; D005576:Colforsin; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D014701:Veratridine; D014700:Verapamil; D012844:Sincalide; D011188:Potassium; D002118:Calcium