“…Many factors including hormones (Nakashima et al, 1971(Nakashima et al, , 1973Kunos, Vermas-Kunos & Nickerson, 1974;Kunos, 1977; Hashimoto & Nakashima, 1978;Hirano, Hashimoto & Nakashima, 1982) and temperature (Endoh, Wagner & Schumann, 1975;Benfey, 1977;Mori, Hashimoto, Hasegawa & Nakashima, 1979) markedly affect the a-adrenoceptor-mediated positive inotropic effect. On the other hand, it has been reported that the responsiveness of the heart to drugs or stress vary with age (Shreiner, Weisfeld & Schock, 1969;Conway, Wheeler & Sannerstedt, 1971;Kronenberg & Drage, 1973;Lakatta, Gerstenblith, Angell, Schock & Weisfeld, 1975;Petrofsky & Lind, 1975;Toda, Fu & Osumi, 1976;Yin, Spurgeon, Raizes, Greene, Weisfeld & Schock, 1976;Gerstenblith, Spurgeon, Froehlich, Weisfeld & Lakatta, 1979;Yin, Spurgeon, Greene, Lakatta & Weisfeld, 1979;Guarnieri, Filburn, Zitnik, Roth & Lakatta, 1980;Toda, 1981). Lakatta et al (1975) and Guarnieri et al (1980) have demonstrated the diminished inotropic response to mature myocardium to catecholamines.…”