Increase in the sensitivity of the vascular smooth muscle to constrictor factors after denervation and with a decrease in blood pressure

The effect of denervation on the contractile activity of the saphenous artery in normotensive rats and rats with regional hypotension was studied. Hypotension was caused by partial occlusion of the abdominal aorta distally from the renal arteries, and then, in four weeks, to denervate the saphenous artery, a portion of the femoral nerve in one of the limbs was resected. In two more weeks, the contractile responses of ring preparations of the saphenous artery (after removal of the endothelium and block of neuronal uptake and β-adrenoreceptors) were investigated under isometric conditions. In normotensive rats, the denervation led to an increase in the vascular sensitivity to norepinephrine, phenylephrine, serotonin, and KCl. Similar changes in contraction were caused by chronic hypotension; however, rats with hypotension exhibited no additional denervation-induced increase in the vascular sensitivity. After treatment with glyoxylic acid, the fluorescence intensity of the vascular adrenergic fibers adapted to a reduced pressure was lower than that in the norm. It was assumed that the vascular hypersensitivity in hypotension is caused by impairment of sympathetic innervation.