Chronotropic and inotropic responses to ASL-7022 on isolated rat atria

ASL-7022 is a new synthetic catecholamine with alpha and beta adrenoceptor stimulating activity having inotropic selectivity in vivo. On the isolated rat atria, ASL-7022 produced concentration-dependent increases in spontaneous rate, developed tension (DT) and maximal velocity of contraction (+T). The maximal chronotropic and inotropic responses to ASL-7022 were similar to those obtained with isoproterenol, although the compound was less potent than isoproterenol. The inotropic and chronotropic effects of ASL-7022 were sensitive to propranolol blockade and were not affected by prazosin blockade. When the inotropic selectivity of ASL-7022 was analyzed, it was found that, like isoproterenol, each concentration of the agonist produced greater chronotropic than inotropic effect. Our results indicate the lack of an alpha 1-mediated component in the chronotropic and inotropic effects of ASL-7022 and the absence of inotropic selectivity in vitro.