Centrally mediated vasopressor effect of angiotensin II in man.

SUMMARY Responses to vertebral and aortic injection of synthetized angiotensin II of the systemic arterial pressure and heart rate were examined in humans and the following results were obtained: Angiotensin II injections in the dosages from 0.016 to 0.06ƒÊg./Kg. caused the following effects. 1) Vertebral injection produced a higher rise in the systemic arterial pressure than that produced by aortic injection of the same dose. 2) Heart rate was increased by vertebral injection of a small dose, but was decreased by aortic injection. From these data, it was considered that vertebral injection of an-giotensin II in humans caused a rise in blood pressure partly by increasing the sympathetic nerve activity. Additional Indexing Words: Vertebral and aortic catheterization investigations have been reported concerning the vasopressor effects of angiotensin II. Angiotensin II has a direct peripheral action on the vascular wall,1), 2) releases catecholamines from the adrenal medulla,3) produces a greater output of noradrenaline at the peripheral nerve endings,4)-8) stimulates directly the post-synaptic neurons in sympathetic ganglia,8) acts on the brain directly or indirectly to increase sympathetic nerve activity and accordingly elevates blood pressure. 11)-13) In our previous study, it was reported that vertebral injection of angiotensin II in rabbit produced a higher rise in blood pressure than that produced by injecting the same dose into the descending thoracic aorta or the internal carotid artery. Moreover, vertebral injection in a small dose produced, although not always, an increase in sympathetic discharge under buffer nerve resection, but aortic injection, on the contrary, produced a decrease in sympathetic discharge.9),15) The present study was carried out to elucidate whether or not a centrally mediated vasopressor effect of angiotensin II exists in humans.