Effects of compound 48/80, a histamine-releasing agent, on accumulation and release of cyclic AMP in various regions of rat brain in vitro.

The effect of compound 48/80 in various rat brain regions - by means of incubating brain sclices with compound 48/80 - on cyclic AMP accumulation and release of the nucleotide into the incubation medium was studied. In all regions tested, accumulation of cyclic AMP occurred within at least 10 min. In the cortex, brain stem and cerebellar regions these increases of cyclic AMP could be blocked by propranolol, a beta-adrenergic antagonist. Diphenhydramin, an antihistaminic agent, was without effect in these regions, but could partially block the compound 48/80-induced rise of cyclic AMP in the hypothalamus. Propranolol had in this region only a moderate blocking effect. Release of cyclic AMP, induced by compound 48/80, occurred in all regions tested and could not be effectively blocked by propranolol or diphenhydramin.