L-Dopa and Cardiac Arrhythmia (Cont.)

To the Editor: I read with interest the letter of Drs. Mars and Krall in the December 16, 1971, issue of the Journal (285:1437, 1971) and should like to call attention to some recent work in our laboratory.¹,² which may be pertinent to their findings and which may explain the arrhythmogenic potential of L-dopa. In experiments using ³H-norepinephrine as a tracer, L-dopa administered to Sprague-Dawley rats resulted in a significant dose-related release of norepinephrine (NE) from the sympathetic nerve endings of the heart. Ganglionic blockade did not prevent the release of cardiac NE, thus indicating a direct effect of L-dopa. No extract is available for articles shorter than 400 words.