Effect of norepinephrine and vasopressin on carotid sinus baroreceptor activity in the anesthetized rabbit.

Norepinephrine (NE) 10(-6) M or vasopressin (VP) 12.5 microU/ml were injected into the isolated carotid sinus of anesthetized rabbits. The sinus was exposed either to the arterial pressure or to a pressure controlled reservoir. Multifiber and single fiber recordings were made. Both NE and VP increased baroreceptor activity at all sinus pressures but decreased activity in a few fibers. The results are consistent with the drugs having their effects on smooth muscle fibers in the adventitia.