Peptidergic Vasodilator Nerves in the Peripheral Circulation and in the Vascular Beds of the Heart and Brain

Abstract

This overview focusses on the ubiquitous presence of immunohistochemically visible peptidergic nerves with vasodilatory function. The nerve fibres are primarily related to the parasympathetic system (vasoactive intestinal polypeptide or VIP), the sympathetic system including the adrenal medulla (enkephalins) and to the sensory system (substance P as well as calcitonin gene-related peptide, CGRP). Substance P and probably also CGRP seem to be the mediators of antidromic vasodilatation. Enkephalins appear to be released both from nerve endings and from the adrenomeduUary cells. The vasodilatory nerve fibres in the heart distribute both to the coronary vessels and to functionally important parts of the myocardium, where interesting relations exist between the peptidergic flow regulation and contractile force. In the brain the sensory and parasympathetic pathways for VIP and substance P/CGRP have recently been mapped in detail, and a new peptidergic intracranial ganglion has been discovered. The selective electrical stimulation of the sensory and post-ganglionic parasympathetic fibres, respectively, in the brain circulation has been found to evoke a pronounced flow increase which does not appear to involve cholinergic mediation. There is also experimental evidence that the mentioned systems of fibres may interact with each other and with the sympathetic nervous system by way of neuronal cross-talk.

Cerebral Blood Flow Regulation by Nitric Oxide: Recent Advances

“…Histochemical studies with antibodies against tyrosine hydroxylase and cholinesterase/choline acetyltransferase have determined the presence of neurons containing these immunoreactivities (Owman, 1990) together with that of NOS Yoshida et al, 1993). There may be cross-talk between nitrergic neurons and adrenergic or cholinergic neurons.…”

The Pharmacology of Nitric Oxide in the Peripheral Nervous System of Blood Vessels

“…Histological studies with antibodies against cholinesterase/choline acetyltransferase and tyrosine hydroxylase have determined the presence of neurons containing these immunoreactivities (Owman 1990), together with that of NOS Yoshida et al, 1993). There may be cross-talk between these neurons of close proximity.…”

Mechanisms of Vasorelaxation

“…Not only is the number of mediators out of hand, but the complexity is magnified by the presynaptic influences of several of the mediators on the activities of other vasoactive nerves. Rather than attempting to consider each of the many neurohumoral, vasodilator mediators, we refer the reader to recent reviews (9,46,47). We will merely describe four recently studied vasodilator systems as examples of this complexity.…”