Cardiac sympathectomy with phenol acutely blunts the postsynaptic adrenergic response

Studies were performed in anesthetized dogs to determine if topical application of phenol to the heart acutely alters postsynaptic function in addition to destroying efferent sympathetic nerves. Left ventricular dP/dt max as well as segment length shortening (%SL) and maximal rate of shortening (dL/dt max) in the circumflex perfusion territory were measured. Responses to left stellate ganglion stimulation (LSS) and intracircumflex injection of norepinephrine (NE, 0.10‐0.50 m̈g) were recorded before and after application of 85% phenol to the atrioventricular junction and to the circumflex artery and its branches (stage 1) as well as to the myocardial surface (stage 2). Responses of dP/dt max, %SL, and dL/dt max to the various dosages of NE were reduced by 40‐64%, 69‐75%, and 44‐61%, respectively, 1 hr after stage 1, indicating that application of phenol to the coronary arteries and arterio‐ventricular junction attenuated the postsynaptic response to adrenergic stimulation. No further changes occurred 1 hr after stage 2. Responses of dP/dt max and dL/dt max to LSS were reduced by 36% and 57%, respectively, after stage 1 and by 75% and 71% after stage 2. Because of high variability, the response of %SL to LSS were not affected by stage 1 or stage 2 application of phenol. In a secondo of 5 dogs, only stage 2 application of phenol was used. The blunting of the LSS response was similar to that seen with stage 1 followed by stage 2, but the NE response was unaffected. These data indicate that application of phenol to the coronary Vessels and to the atrioventricular junction acutely blunts both the postsynaptic response to afferent nerve stimulation, while application of phenol to the myocardial surface blunts only the response to efferent nerve stimulation. Thus, in acute animal studies, application of phenol to the myocardial surface may provide more reliable result on the effects of ventricular denervation.