REGULATION OF ADENYLATE-CYCLASE BY GALANIN, NEUROPEPTIDE-Y, SECRETIN AND VASOACTIVE INTESTINAL POLYPEPTIDE IN RAT FRONTAL-CORTEX, HIPPOCAMPUS AND HYPOTHALAMUS

This study characterizes regional regulation of adenylate cyclase by g alanin, neuropeptide Y (NPY), secretin and vasoactive intestinal pepti de (VIP) in rat brain frontal cortex, hypothalamus and hippocampus. In our experimental system, galanin caused small detectable activation ( 10-20%) of basal adenylate cyclase activity in frontal cortex and hipp ocampus but had no effect on basal adenylate cyclase activity in hypot hatamus. Galanin inhibited forskolin-stimulated adenylate cyclase in a ll three brain regions - hypothalamus, hippocampus and frontal cortex by 54.5%, 44.3% and 25.7%, respectively. NPY reduced basal and forskol in-stimulated enzyme activities by 35% only in frontal cortex, but not in the other two brain areas. Secretin had no effect in frontal corte x but caused similar adenylate cyclase activation in hypothalamus and hippocampus. VIP had a stimulatory effect of 32.8% and 32.4% in fronta l cortex and hippocampus, respectively. The results indicate regional differences in adenylate cyclase modulation by the four peptides and r eveal interesting relations in comparison with peptide and receptor de nsities in the three investigated brain regions.