title: A comparison of the augmentation of H1 and H2 receptor agonist stimulation of rabbit atrial chronotropic response by two phosphodiesterase inhibitors, papaverine and theophylline.
abstract: Papaverine and theophylline both increase the chronotropic response of isolated rabbit atria, however, the maximum stimulation following papaverine is much smaller than that obtained with theophylline. When these phosphodiesterase inhibitors are used in conjunction with histamine (H1 and H2 receptor agonist), 2-(2-aminoethyl) pyrazole (H2 agonist) and 3-(2-aminoethyl) triazole (H1 agonist) the responses are all considerably more than additive. This suggests that both H1 and H2 histamine receptors can activate adenyl cyclase and therefore increase the formation of cyclic AMP in spite of reports that only H2 receptors stimulate adenyl cyclase.
mesh_terms: D000818:Animals; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D010208:Papaverine / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011817:Rabbits; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D013806:Theophylline / Q000494:pharmacology*; D013997:Time Factors; D014230:Triazoles / Q000494:pharmacology
chemical_list: D010726:Phosphodiesterase Inhibitors; D011720:Pyrazoles; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D014230:Triazoles; D013806:Theophylline; D010208:Papaverine