INNERVATION OF THE HUMAN MIDDLE MENINGEAL ARTERY - IMMUNOHISTOCHEMISTRY, ULTRASTRUCTURE, AND ROLE OF ENDOTHELIUM FOR VASOMOTILITY

The majority of nerve fibers in the middle meningeal artery and branch ing arterioles are sympathetic, storing norepinephrine and neuropeptid e Y (NPY). A sparse supply of fibers contain acetylcholinesterase acti vity and immunoreactivity toward vasoactive intestinal peptide (VIP), peptidine histidine methionine (PHM), and calcitonin gene-related pept ide (CGRP). Only few substance P and neuropeptide K immunoreactive fib ers are noted. Electronmicroscopy shows axons and terminals at the adv entitial medial border of the human middle meningeal artery, with a fa irly large distance to the smooth muscle cells (>500 nM). Several axon profiles contain vesicles of different types, including putative sens ory profiles. The perivascularly stored signal substances, norepinephr ine and NPY induced vasoconstrictor. Relaxations were induced by acety lcholine and substance P, and these were significantly reduced in arte ries without endothelium, while the responses to norepinephrine, NPY, VIP, PHM, and CORP were not changed by endothelium removal. Blockade e xperiments showed that the vasomotor responses to norepinephrine were blocked by prazosin, to NPY by BLBP 3226, acetylcholine by atropin, su bstance P by RP 67580, and the human alpha-CGRP response by human alph a-CGRP(8-37). (C) 1998 Elsevier Science Inc.