Sympathetic denervation of resistance arteries increases contraction and decreases relaxation to flow.
The effect of chronic sympathetic and possibly sensory denervation on flow-induced changes in smooth muscle tone was examined in a branch of the rabbit ear artery (200-400 microns ID). The superior cervical ganglion and 1-cm portions of the greater and anterior auricular nerves were removed from 4-wk-old rabbits while under general anesthesia, and arterial segments were studied 21 days later. Efficacy of denervation was assessed by catecholamine histochemistry and by absence of a constrictor response to transmural electrical field stimulation. Intraluminal flow of physiological saline solution was made through a pipette into matched-innervated and -denervated segments. Flow-induced contraction was increased in the denervated compared with the contralateral innervated segments. At the lowest flow rate studied (1 microliters/min), the contraction increased more than six times. This is consistent with the previously described nonspecific, nondeviational hypersensitivity of denervated vascular smooth muscle to constrictor influences. By contrast flow-related dilation at 10 and 20 microliters/min was significantly diminished. An intraluminal flow rate could be found that resulted in dilation in innervated but not the matched-denervated segments. Endothelial-mediated dilation to acetylcholine was also impaired. Chronic sympathetic denervation increased the magnitude of flow contraction and decreased that of flow relaxation.
Bevan
R D
RD
Department of Pharmacology, Vermont Center for Vascular Research, College of Medicine, University of Vermont, Burlington 05405.
Clementson
A
A
Joyce
E
E
Bevan
J A
JA
D000818:Animals; D001158:Arteries / Q000294:innervation* / Q000502:physiology; D004423:Ear / Q000098:blood supply; D011817:Rabbits; D012039:Regional Blood Flow; D013562:Sympathectomy; D014655:Vascular Resistance; D014661:Vasoconstriction / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*