THE PEPTIDERGIC INNERVATION OF THE HUMAN SUPERFICIAL TEMPORAL ARTERY - IMMUNOHISTOCHEMISTRY, ULTRASTRUCTURE, AND VASOMOTILITY

The peptidergic innervation of the human superficial temporal artery w as investigated by means of immunohistochemical, ultrastructural, and in vitro pharmacological techniques. A dense network of nerve fibers w as found in the adventitia. The majority of the nerve fibers displayed immunoreactivity for tyrosine hydroxylase and neuropeptide Y (NPY). A moderate supply of perivascular nerve fibers displayed either acetylc holinesterase activity or immunoreactivity for vasoactive intestinal p eptide (VIP), peptide histidine methionine-27 (PHM), and calcitonin ge ne-related peptide (CGRP). Only a few nerve fibers displayed substance P (SP), neurokinin A (NKA), and neuropeptide K (NPK) immunoreactivity . In double immunostained preparations, SP immunoreactivity was co-loc alized with NPK and CGRP in the same nerve fibers. Ultrastructural stu dies revealed the presence of numerous axon variocosities at the adven titial-medial border. NPY, VIP, and CGRP immuno-reactivities occurred in the same type of large granular vesicles, but in morphological dist inct nerve profiles. NPY had, in general, no direct vasoconstrictor ef fect. However, at a low concentration of NPY contractile response indu ced by NA (10(-7)-10(-6) M) was 9-15 times enhanced. The NPY-induced p otentiation of the NA-induced contraction was nor dependent on the pre sence of an intact endothelium. No significant difference was found be tween acetylcholine, VIP, and PHM in either potency or degree of relax ation. SP, NKA, and CGRP also acted as vasodilatory agents, with CGRP being more potent than the tachykinins. The response to SP, but not CG RP, was dependent on an intact endothelium. Pretreatment of the vessel s with a low concentration of NPY did not change the responses to ACh, VIP, SP, or CGRP.