Rat gastric mucosal cAMP and cGMP after adrenergic stimulation and blockade

The effect of adrenergic stimulation and blockade on the concentration of cAMP and cGMP was studied in the rat gastric mucosa. Adrenaline (0.5-2.0 mg/kg) elevated the gastric mucosal cAMP and cGMP levels up to 100% in a dose-dependent manner. Blockade of the beta-adrenoceptors with 4 mg/kg propranolol suppressed the adrenaline effect on the cAMP level and increased the effect on the cGMP concentration up to 500%. The opposite effect was found under alpha-adrenoceptor blockade. Phenoxybenzamine, 4 mg/kg, prevented the adrenaline effect on the cGMP level and increased the effect on the cAMP concentration up to 300%. Predominant stimulation of the beta-adrenoceptors by isoproterenol or of the alpha-adrenoceptors by phenylephrine caused smaller changes in the cyclic nucleotide concentration than did adrenaline. Their effect was more pronounced when the non-stimulated receptor was blocked. The data indicate that the rat gastric mucosa contains alpha- and beta-adrenoceptors. The effect of adrenaline on the gastric mucosal cAMP level is mediated by beta-adrenoceptors and that on the cGMP level by alpha-adrenoceptors.