SUPERSENSITIVITY IN RAT MICRO-ARTERIES AFTER SHORT-TERM DENERVATION

Contractile responses to phenylephrine acid high-K+ were investigated in vitro in microvascular preparations from the rat medial plantar art ery. a branch from the saphenous artery, obtained after short-term den ervation in vivo. Two groups of animals were studied: (1) animals unde rgoing surgical resection of the saphenous nerve, and (2) animals unde rgoing surgical resection of both the sciatic and saphenous nerves. Th e animals were operated on one side only. Microvascular preparations ( diameter about 325 mu m) were obtained 10 days after surgery. Vessels from the non-operated side served as controls. Immunocytochemistry sho wed a decreased number of both neuropeptide Y (NPY) and calcitonin gen e-related peptide (CGRP) immunoreactive nerve fibres in vessels after resection of the saphenous nerve only. Resection of both the saphenous and the sciatic nerve caused a complete loss of immunoreactive nerve fibres. Mechanical measurements were performed using a wire myograph. In vessels subjected to resection of the saphenous nerve the sensitivi ty to phenylephrine was similar to controls. Vessels denervated by res ection of both the saphenous acid sciatic nerves showed significant in creases in phenylephrine and potassium sensitivity. When depolarized i n high-K+ solution the denervated vessels showed an increased sensitiv ity to extracellular Ca2+. The results show that complete short-term d enervation of the rat medial plantar artery in vivo causes a pronounce d supersensitivity in the vascular smooth muscle. The supersensitivity appears not to be restricted to the sympathetic alpha-receptors but a lso associated with changes in the cellular excitation-contraction cou pling. Such altered reactivity of the vascular smooth muscle may contr ibute to vascular disturbances observed in vivo after nerve damage or surgical denervation.