Histamine-and isoprenaline-evoked stimulation of cAMP formation in chick cerebral cortex.

Histamine (HA) and isoprenaline (ISO) strongly stimulated cAMP formation in chick cerebral cortical slices. The effects of HA and ISO were selectively antagonized by HA H2-receptor blockers (aminopotentidine, ranitidine) and beta-adrenoceptor blocker propranolol, respectively. The combination of HA (0.1-100 microM) and ISO (0.1-10 microM) produced some additive effects when the drugs were used at low concentrations, i.e. 0.1-1 microM but not when HA was applied at 10 or 100 microM doses (which evoked nearly maximal effect). It is suggested that HA H2-like receptors and beta-adrenoceptors (whose activation leads to stimulation of cAMP formation) are localized in the same subpopulation of cortical cells, in which they probably utilize a common and limited pool of cAMP-generating system.