“…The confusion appears to be due, at least in part, to the fact that different regions of the heart respond to ATP in different ways (see Drury, 1936). Its chronotropic and inotropic effects are predominantly negative on isolated mammalian atria (dog: Emmelin & Feldberg, 1948;cat: Green & Stoner, 1950; Acierno, Burno, Burnstein & Di Palma, 1952;Bertelli, Bianchi & Beani, 1972; rabbit: Bielschowsky, Green & Stoner, 1946; Emmelin & Feldberg, 1948; Bertelli et al 1972;rat: Hollander & Webb, 1957;Bertelli et al 1972;Meinertz, Nawrath & Scholz, 1973), but positive on both mammalian (rabbit: Green & Stoner, 1950: Gillespie, 1934) and amphibian (Lindner & Rigler, 1931;Lichtneckert & Straub, 1949;Loewi, 1949;Marshall & Andrus, 1953;Szent Gy6rgyi, 1953; Kanda, Sekiya & Inoue, 1954;Schenberg, 1956; Versprille, 1963Versprille, , 1965Boyd & Forrester, 1968) ventricles. Not surprisingly, then, the responses to ATP of isolated whole hearts, and those produced by injection into intact animals, are complex (cats: Bielschowsky et al 1946;Emmelin & Feldberg, 1948;Green & Stoner, 1950;dogs: Emmelin & Feldberg, 1948;Angelakos & Glassman, 1961; rabbit : Sydow & Ahlquist, 1954;Buckley, Tsuboi & Zeig, 1961; guinea-pig: Rand, Stafford & Thorp, 1955;rat: Versprille & Van Duyn, 1966; man: Wayne, Goodwin & Stoner, 1949).…”