INNERVATION OF HUMAN EPICARDIAL CORONARY VEINS - IMMUNOHISTOCHEMISTRYAND VASOMOTILITY

Objective: The aim was to investigate the innervation and vasomotor re sponses to classical and putative transmitters of the coronary venous bed. Methods: The innervation of human epicardial coronary veins was i nvestigated using acetylcholinesterase histochemistry and immunofluore scence staining, together with antisera against the general neuronal m arker protein gene product 9.5 (PGP 9.5), the catecholamine synthesisi ng enzyme tyrosine hydroxylase, and neuropeptides [neuropeptide Y, vas oactive intestinal peptide (VIP), substance P, and calcitonin gene rel ated peptide (CGRP)]. The vasomotor responses to noradrenaline, acetyl choline, neuropeptide Y, substance P human alpha calcitonin gene relat ed peptide (alpha CGRP), and VIP were tested on isolated circular huma n epicardial coronary vein segments. Results: A network of nerve fibre s was shown in the major epicardial coronary veins by means of an anti serum to PGP 9.5. The majority of the perivascular nerve fibres posses sed neuropeptide Y and tyrosine hydroxylase immunoreactivity. Only a f ew nerve fibres displayed substance P, CGRP, and VIP immunoreactivity and acetylcholinesterase activity. Noradrenaline and acetylcholine ind uced powerful contractions of all the tested segments, whereas no cont raction was induced by neuropeptide Y, alpha CGRP, substance P, or VIP . All segments precontracted with U46619 responded with potent relaxat ion to alpha CGRP, substance P, and VIP, whereas noradrenaline and ace tylcholine only in low concentrations induced weak relaxation of a few of the segments. No relaxation was induced by neuropeptide Y. Conclus ions: This is the first study to demonstrate comprehensively the periv ascular innervation of human coronary veins and corresponding vasomoto r effects, suggesting a role in regulation of the coronary venous circ ulation.