Effect of the H1-histamine-like agonist material extracted from bovine spleen on 3': 5'-cyclic nucleotides content in guinea-pig ileal smooth muscle

The effect of a water-soluble "histamine-free" splenic material that mimics the H1-receptor mediated contractile action of histamine on the guinea-pig ileum has been studied upon concentrations of cGMP and cAMP in slices of this smooth muscle preparation. The splenic extract induced a rapid and sustained decrease in the concentration of cGMP accompanied by a slow decrease in cAMP content in the ileal tissue. These results indicate that the smooth muscle-stimulating agent in splenic extract had no increasing effect on cGMP content as could be expected from the hypothesis that cGMP and cAMP might mediate the smooth muscle contraction and relaxation respectively. The data are not compatible with the general hypothesis that the action of histamine and histamine-like agonists on H1-receptors is associated with an increased concentration of cGMP.