Histamine (HI) potently stimulated, through H2-receptors, cAMP accumulation in rabbit cerebral cortical slices but not in retinal pieces. The action of HI in the cerebral cortex was not significantly affected by dopamine, serotonin, melatonin and GABA-ergic drugs. Forskolin markedly stimulated cAMP accumulation both in the cerebral cortex and retina. There was a synergistic interaction between HI and forskolin in the cerebral cortex, whereas in the retina HI decreased the forskolin-activated cAMP accumulation.

Histamine (HI) potently stimulated, through H2-receptors, cAMP accumulation in slices of the rabbit cerebral cortex (EC50: 15 microM; maximum stimulation: 300-450% of the basal level). Combination of L-noradrenaline or L-adrenaline and adenosine with HI showed synergistic and additive effects, respectively. Carbachol, arecoline and pilocarpine had no effect, while oxotremorine and tremorine increased and decreased the HI response when used at low or high concentrations, respectively.