Abstract
In the foregoing report Matsuo and Tachi (1) showed that though the isolated atrium of rabbit which was beating in vitro took up considerable amounts of noradrenaline added to the bath fluid, the content of noradrenaline of the restarted atrium by addition of noradrenaline did not significantly differ from the reduced content of noradrenaline of the atrium which was ceased to beat by addition of 10-6 of reserpine. From the results the authors suggested that the restarting effect derived from the pharmacological action of the catecholamine and not from the biochemical binding of catecholamine to the storage site. The role of the dopa-decarboxylase in noradrenaline synthesis was substantiated with the demonstration of the conversion of dopa and of dopamine to noradrenaline (2-3). In this report the effects of dopa and dopamine were studied on the spontaneous contraction, transmembrane potentials and content of noradrenaline in the isolated rabbit's atrium which had been depressed or abolished the spontaneous activity and depleted the content of noradrenaline by reserpine.
