The impact of aging on vasa nervorum, nerve blood flow and vasopressin responsiveness

Abstract

Objective: Aging impacts microvessels in a number of tissue beds. Vasopressin acts as a vasoconstrictor in most blood vessels but may also cause vasodilation. We evaluated the role of aging and vasopressin in the regulation of nerve blood flow (NBF) in rat peripheral nerve. Methods: We undertook a dose-response study to examine the impact of aging on resting NBF and its vasoreactivity to vasopressin. Nerve blood flow was measured using microelectrode hydrogen polarography. Argininevasopressin was administered both intra-arterially and topically. Results: In young adult rats (two months old) topical epineurial application of arginine-vasopressin produced a concentration-dependent reduction of NBF (ED50= 3.8 X 10-5 mol/L). Intra-arterial arginine-vasopressin also reduced NBF. Nerve blood flow was lower in aged rats (12 months old) and less responsive to topically applied vasopressin. The aging group had significantly higher concentrations of vasopressin in plasma than did the younger group. Conclusions: The results suggest that vasopressin constricts vessels in peripheral nerve and that there is an age related decline in the vasoconstrictive response to vasopressin. There may be a reduction in receptor sensitivity in vascular smooth muscle cells in peripheral nerve with increasing age.