Surgical sympathectomy of the heart in rodents and its effect on sensitivity to agonists.

A new procedure for sympathetic denervation of the hearts of rats and guinea pigs is described. Bilateral removal of the inferior and medial cervical ganglia results in almost complete loss of catecholamines from atria and ventricles, disappearance of catecholamine-associated histofluorescence from the region of the sinoatrial node and marked depression of the chronotropic concentration-response curve for tyramine in right atria of both species. Seven days after bilateral sympathectomy, the chronotropic concentration-response curve for isoproterenol is shifted to the left by a factor of 3.3 in the rat and 1.7 in guinea-pig right atria. The chronotropic concentration-response curve for histamine was not shifted by sympathectomy in the guinea-pig right atrium. Inasmuch as the rat atrium does not respond to histamine, similar experiments could not be done in the rat. The inotropic concentration-response curve for isoproterenol in electrically driven left atria was not affected by 7 days of sympathectomy in either species. These results indicate that chronic surgical sympathectomy of the heart can be successfully accomplished in the rat and guinea pig. Such sympathectomy induces a postjunctional supersensitivity in guinea-pig right atria which is qualitatively and quantitatively similar to that described previously for chronic treatment with reserpine. Bilateral surgical sympathectomy provides a valuable tool for future investigations of the cellular basis of supersensitivity in the myocardium.