NEUROTRANSMITTER REGULATION OF SOMATOSTATIN SECRETION BY FETAL-RAT CEREBRAL CORTICAL-CELLS IN CULTURE

Extensive studies exploring the regulation of hypothalamic somatostati n GHRIH release have been reported, but the factors regulating GHRIH r elease in the cerebral cortex have not been well defined. We have stud ied the effects of central neurotransmitters on GHRIH secretion by cul tured fetal rat cerebral cortical cells and on intracellular GHRIH lev els. Cells maintained in vitro for 15-20 days were incubated with dopa mine (DA), acetylcholine (ACh), gamma-aminobutyric acid (GABA), norepi nephrine (NE), serotonin (SE) or histamine (His) (10(-11) M to 10(3) M ) for 30 minutes. Following incubation, immunoreactive GHRIH was measu red by RIA in cell extracts and incubation media. DA increased intrace llular GHRIH content but have no effect on GHRIH in the media. Both me dia and intracellular GHRIH content were significantly reduced by GABA and SE. The effect of NE was stimulatory at low (10(-9) M) and inhibi tory at high (10(-5) M to 10(-3) M) concentrations. ACh was found to i ncrease media GHRIH and to decrease intracellular GHRIH content; 30 mi n exposure to His did not significantly modify either media or intrace llular GHRH. Our findings with fetal rat cerebral cortical cells in cu lture demonstrate that endogenous neurotransmitters do have the capaci ty to directly influence GHRIH regulation.