THE "HUMORAL" COMPONENT OF THE PRESSOR RESPONSE TO CENTRAL VAGAL STIMULATION AND THE IDENTIFICATION OF THE "HUMOR" AS NOREPINEPHRINE

¹ Department of Medicine, Cardiac Laboratory and Departments of Physiology, and Pharmacology, University of Cincinnati, College of Medicine, Cincinnati, Ohio

It is widely held that the pressor response to central vagal stimulation (CVS) results from efferent sympathetic impulses arising in the central nervous system. Although evidence has been presented that humoral agents contribute to the pressor response, it is not clear how frequently pressor agents are released and what agents are involved. By using an extracorporeal bypass to perfuse the innervated kidney, the neurogenic and the "humor" response to CVS were separated. Applying strong stimuli, presser responses of the general and renal circulation could be obtained regularly. The "humoral" response to CVS occurred in all dogs (34 experiments). The presser agent contained in the arterial plasma during the "humoral" response to CVS was identified as norepinephrine. Norepinephrine, therefore, is responsible for both pressor responses to CVS: it is released locally from the sympathetic nerve terminals (neurogenic response), and it becomes blood-borne and causes the delayed "humoral" response.