SUPERSENSITIVITY TO L-NOREPINEPHRINE OF THE DENERVATED SINOATRIAL NODE.

Abstract

Following attempted denervation of the heart by the technic of regional neural ablation, dogs with incomplete cardiac denervation were shown to have the same supersensitivity to l-norepinephrine as dogs in which the denervation of the heart was complete. Dogs with chronic bilateral stellate ganglionectomy or those pretreated with reserpine had cardiac acceleration in response to the administration of tyramine or to stimulation of the stellate cardiac nerves, but did not demonstrate supersensitivity to l-norepinephrine. No supersensitivity was seen in dogs with chronic bilateral cervical vagotomy. Excision of the right stellate and caudal cervical ganglia and the immediately adjacent right vagus nerve resulted in supersensitivity to l-norepinephrine. In these animals cardiac acceleration resulted from stimulation of the left stellate cardiac nerves or from the administration of tyramine. The supersensitivity was lost after excision of the sinoatrial node. It is concluded that one can uniquely denervate the sinus node and that dogs so treated will develop supersensitivity to l-norepinephrine despite the presence of functional sympathetic nerves to the rest of the heart.