Effects of Dopamine and Dopa on the Isolated Rabbit’s Atrium Treated With Reserpine

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 nor adrenaline did not significantly differ from the reduced content of noradrenaline of the atrium which was ceased to beat by addition of 10 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 n9radrenaline (2-3). In this report the effects of dopa and dopamine were studied on the spontaneous contraction, transme_mbrane 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.

The Effects of Reserpine on the Spontaneous Contraction of the Isolated Atrium of Rabbit Treated With Monoamine Oxidase Inhibitors

“…When the atrium depressed by in vitro reserpine was restarted by addition of noradrenaline, adrenaline, dopa or dopamine, the content of noradrenaline remained unchanged (2,3). From these results Matsuo and Tachi (2) and Tachi et al (3) suggested that the depressant effect of reserpine in vitro on the spontaneous contraction of the atrium might not cor relate with the depletion of noradrenaline.…”

“…On the other hand, reserpine in vitro to the atrium isolated from the normal rabbit depressed and finally abolished the rhythmic contraction and transmembrane potential (1-4) with only 20 to 30% reduction of noradrenaline (11). When the atrium depressed by in vitro reserpine was restarted by addition of noradrenaline, adrenaline, dopa or dopamine, the content of noradrenaline remained unchanged (2,3). From these results Matsuo and Tachi (2) and Tachi et al (3) suggested that the depressant effect of reserpine in vitro on the spontaneous contraction of the atrium might not cor relate with the depletion of noradrenaline.…”

The MODIFICATION OF INOTROPIC ACTION OF OUABAIN BY 6-Hydroxydopamine AND Α-Methyl-P-Tyrosine IN DOGS

“…Attenuation of glycoside action following reserpine may therefore result from effects un related to its catecholamine depleting action (9,10,11,12).…”