Functional evidence against the existence of β2-adrenoceptors mediating positive inotropic effects in guinea-pig right ventricular myocardium

In guinea-pig isolated papillary muscles we studied the positive inotropic effects of the beta-adrenoceptor agonists isoprenaline, fenoterol and noradrenaline in the presence and absence of the beta 1-selective antagonist atenolol and the beta 2-adrenoceptor antagonist ICI 118.551. In Schild regression analysis pA2 values, for either atenolol (7.14-7.16) and ICI 118.551 (6.79-6.84) were independent of the agonists used. These results support the view that the inotropic response in guinea-pig ventricular myocardium is mediated by beta 1-adrenoceptors only.