ISSN:1018-1172    

DOI:10.1159/000158796

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158797

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158798

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

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.

ISSN:1018-1172    

DOI:10.1159/000158799

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Intracoronary infusion of acetylcholine produces a prompt increase in coronary blood flow in dogs, but a paradoxical decrease has been reported in baboons and cattle. The action of acetylcholine was reexamined in anesthetized dogs, baboons and goats, with the coronary circulation pump perfused at constant pressure and the heart rate held constant with electrical pacing. Intracoronary infusions of low doses of acetylcholine produced coronary vasodilatation and an increase in coronary venous oxygen tension without a change in cardiac contractility (dP/dt) or myocardial oxygen consumption in all three species. High doses of acetylcholine produced coronary vasodilatation only in dogs, but resulted in a decrease in cardiac contractility and myocardial oxygen consumption accompanied by a decrease in coronary flow in baboons and goats. It is concluded that low doses of acetylcholine produce coronary vasodilatation in all three species, and that the decrease in coronary blood flow observed in baboons and goats at high doses is probably due to local metabolic vasoconstriction secondary to the negative inotropic effects of acetylcholine.

ISSN:1018-1172    

DOI:10.1159/000158800

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

At low concentrations and in physiologic states vasopressin is a potent antidiuretic hormone. Its cardiovascular effects have been more complex and their role in circulatory adjustments to hypovolemia and hypotension difficult to define with precision. Although recognized as a powerful vasoconstrictor, its pressor effect in intact animals, even at high concentrations, is minimal. The reasons for this blunted pressor response have been explored. This report is a review of previously published work from our laboratories which highlights the direct and indirect vasodilator actions of this hormone in animals and humans. The indirect vasodilator effect is caused by inhibition of sympathetic efferents, and facilitation of the baroreflex through a central action of the hormone and its sensitization of arterial baroreceptors as well as cardiac afferents.

ISSN:1018-1172    

DOI:10.1159/000158801

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

In vitro investigations have identified three major mechanisms which could contribute to the vasodilator action of serotonin (5-hydroxytryptamine, 5-HT): direct vascular smooth muscle relaxation; prejunctional inhibition of noradrenaline release from vascular sympathetic nerve terminals; and release of endothelium-derived relaxing factor (EDRF). In vivo studies have shown that in pig and cat common carotid circulations, rabbit hind-quarter and mesenteric circulations, and rat systemic vasculature, direct vascular smooth muscle relaxation may be the predominant mechanism involved, but the contribution of EDRF release remains to be established. In other circulations in vivo (dog femoral and common carotid), prejunctional inhibition of vascular sympathetic tone is the predominant mechanism responsible for serotonin-induced vasodilatation. All of these actions are mediated by 5-HT1-like receptors, but different subtypes seem to be involved in each of these mechanisms. The prejunctional inhibitory receptor has been the most studied; depending on the tissue, these subtypes may resemble 5-HT1A, 5-HT1B, 5-HT1c or 5-HT1D binding sites, or the contractile receptor in dog saphenous vein.

ISSN:1018-1172    

DOI:10.1159/000158802

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Bovine mesenteric lymphatic vessels have nerves in their walls which in response to field stimulation cause an increase in freqency of spontaneous lymphatic contractions and this could be blocked by α-antagonists. When vessels were loaded with [3H]-noradrenaline, 3H-effiux was increased in response to field stimulation and this was potentiated by α2-antagonists and depressed by α2-agonists. Electrical activity in these vessels consisted of a single action potential which preceded each contraction. Mean resting potential was –61 mV ± 5.7 (SD). Stimulation of postsynaptic α-receptors caused a depolarization accompanied by a decrease in membrane conductance while β-receptor stimulation had the opposite effect. Lymphatic noradrenergic nerves appear to have a role in the living animal since stimulation of the sympathetic chain in anaesthetized sheep increased popliteal efferent lymph flow and this could be blocked by α-adrenergic

ISSN:1018-1172    

DOI:10.1159/000158803

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Peptides act as vasoconstrictors (for instance angiotensins, vasopressin) or vasodilators (the kinins, the neurokinins), both through direct activation of specific receptors in the vascular smooth muscles or indirectly through the release of other endogenous inhibitors of the vascular tone. Kinins and neurokinins as well as their multiple receptors have been analyzed in the present study to assess the possible contributions of peptides to vasodilatation. Kinin receptors, B1 and B2, have been characterized, using new selective agonists and antagonists. B1 and B2 receptors appear to present in endothelium (B2) and in smooth muscles (B2, B1) of a variety of isolated vessels of the dog and the rabbit, where they subserve both stimulatory and inhibitory effects. Vasodilator inhibitory mechanisms depend on the release of the endothelium-relaxing factor and/or of prostanoids from the endothelium or the smooth muscles, especially in the dog renal vessels, where both B1and B2 receptors appear to be involved in causing vasodilatation. B2 receptors have also been shown to activate cardiovascular reflexes through a direct action on sensory fibers or on reflexogenic areas of the epicardium. Three types of receptors for neurokinins, namely NK-1, NK-2 and NK-3, have been identified by the use of naturally occurring peptides and of some analogues that act as selective agonists of a single receptor type. NK-1 receptors (particularly sensitive to substance P) have been shown to be present in endothelia where they promote the release of the endothelium relaxing factor, while NK-2 receptors (sensitive to neurokinin A) are found in the pulmonary artery of the rabbit and act directly to contract the smooth muscle. NK-3 receptors (sensitive to neurokinin B) may be present in the veins where they act as venoconstrictors, increasing also the vascular permeability. Thus, peptides and their receptors participate through various mechanisms in the regulation of vascular tone and peripheral blood flow.

ISSN:1018-1172    

DOI:10.1159/000158804

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

In vitro experiments on vascular smooth muscle often fail to reveal phenomena clearly demonstrable in vivo. Several recent observations in our laboratory have revealed the facility to uncover responses mediated by receptors whose functional expression had remained hidden with the standard experimental conditions first employed: conversely manipulation of conditions can selectively hide a particular receptor’s response. Examples include the uncovering of responses to: 5HT1 receptors by raised O2 tension (via cyclooxygenase products) in human umbilical vessels; α2-adrenoceptors in rabbit saphenous artery by angiotensin II and α2-adrenoceptors in perfused rat tail by elevating tone with vasopressin. The powerful synergism of agonists which cannot on their own cause contraction, can lead to inaccurate interpretations of agonist-antagonist interactions. Finally, the influence of tissue metabolism on receptor expression clearly illustrates the complex processes which must be involved in v

ISSN:1018-1172    

DOI:10.1159/000158805

出版商:S. Karger AG    

年代:1990

数据来源: Karger