Abstract
To investigate the physiological role of the sympathetic innervation of the carotid sinus, an attempt was made to find whether denervation sensitization of the carotid sinus would occur 2 weeks after the resection of the sympathetic nerve supply or not. The changes in sensitivity to noradrenaline weree examined by injecting 5-25 gamma of noradrenaline directly into the adventitia of the denervated carotid sinus. The resulting fall in blood pressure and the changes in the carotid occlusion reflexes were compared with those following the injection of the same dose of noradrenaline into the adventitia of the innervated side.
The responses to 5-50 gamma of noradrenaline injected directly into the adventitia of the carotid sinus area were variable in normal pentobarbital anesthetized dogs, and the doses less than 20 gamma of noradrenaline did not show the systemic hypotension and the depression of the carotid sinus reflexes in these dogs.
In the cervical-sympathectomized dogs, 5-25 gamma of noradrenaline applied locally on the denervated side induced the typical blood pressure fall and the depression of the carotid occlusion reflexes in almost all the experiments, while these typical responses were not found by the application of noradrenaline to the innervated carotid sinus.
Angiotensin did not show such responses by the local application to the denervated carotid sinus.
Thus, evidence of supersensitivity was obtained by the local application of 5-25 gamma of noradrenaline to the denervated carotid sinus area. The sympathetic innervation of the carotid sinus seemed to be significant.
