Evidence for an increase in adrenergic nerve function in blood vessels from experimental hypertensive rabbits

The possibility of changes in the adrenergic innervation of blood vessels in experimental hypertension was investigated by measuring arterial norepinephrine content, neuronal uptake of norepinephrine, and the neurogenic contractile response in rabbits made hypertensive by partial constriction of the abdominal aorta proximal to the kidneys. Two to 3 weeks after surgery, norepinephrine content was increased in the arteries above the ligature, where arterial blood pressure was increased, but not in the arteries below the ligature, where arterial blood pressure was normal, in the heart, or in the veins. Neuronal norepinephrine uptake per unit length of vessel and the neurogenic contractile response increased with the rise in arterial blood pressure. The neurogenic contractile response can be taken as an indication of an increase in transmitter release. The results taken together suggest an increase in the function and possibly the amount of the adrenergic neuroneal terminal in hypertension. Since the distributions of the changes in the adrenergic innervation and the increases in smooth muscle cell proliferation in hypertension are similar, these two processes may be interrelated.