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Titolo:
RELATIONSHIP BETWEEN IMIDAZOLINE AND ALPHA(2)-ADRENOCEPTORS INVOLVED IN THE SYMPATHOINHIBITORY ACTIONS OF CENTRALLY ACTING ANTIHYPERTENSIVEAGENTS
Autore:
HEAD GA; CHAN CKS; BURKE SL;
Indirizzi:
BAKER MED RES INST,COMMERCIAL RD PRAHAN,POB 6492 MELBOURNE VIC 8008 AUSTRALIA BAKER MED RES INST,NEUROPHARMACOL LAB PRAHRAN VIC 3181 AUSTRALIA
Titolo Testata:
Journal of the autonomic nervous system
fascicolo: 2-3, volume: 72, anno: 1998,
pagine: 163 - 169
SICI:
0165-1838(1998)72:2-3<163:RBIAAI>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
CONSCIOUS RABBITS; CARDIOVASCULAR ACTIONS; HYPOTENSIVE ACTION; ALPHA-METHYLDOPA; BLOOD-PRESSURE; BINDING-SITES; CLONIDINE; RILMENIDINE; RECEPTORS; MOXONIDINE;
Keywords:
IMIDAZOLINE RECEPTORS; ALPHA(2)-ADRENOCEPTORS; CLONIDINE; RILMENIDINE; MOXONIDINE ALPHA-METHYLNORADRENALINE; IDAZOXAN; CENTRAL NORADRENERGIC NEURONS; ROSTROVENTROLATERAL MEDULLA;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
40
Recensione:
Indirizzi per estratti:
Citazione:
G.A. Head et al., "RELATIONSHIP BETWEEN IMIDAZOLINE AND ALPHA(2)-ADRENOCEPTORS INVOLVED IN THE SYMPATHOINHIBITORY ACTIONS OF CENTRALLY ACTING ANTIHYPERTENSIVEAGENTS", Journal of the autonomic nervous system, 72(2-3), 1998, pp. 163-169

Abstract

Since the first suggestion of the existence of imidazoline receptors,there has been a continuing and yet unresolved debate as to their contribution to the antihypertensive actions of clonidine-like agents. Inthis review we bring together a number of studies from our laboratorywhich have examined the importance and interdependence of imidazolinereceptors and alpha(2)-adrenoceptors in the mechanism of action of centrally acting antihypertensive drugs. Using conscious rabbits and a range of imidazoline and specific alpha(2)-adrenoceptor antagonists we have consistently found that second generation agents rilmenidine and moxonidine preferentially act via imidazoline receptors but that alpha(2)-adrenoceptors are important for the hypotension produced by clonidine and ol-methyldopa. Despite this difference in receptor mechanism, the hypotension produced by all these drugs is dependent on central noradrenergic pathways. In other studies using anaesthetised rabbits anddirect measures of sympathetic nerve activity we confirmed the generally held view that the major site of sympatho-inhibitory actions and sympathetic baroreflex effects of centrally acting antihypertensive agents is the rostral ventrolateral medulla (RVLM). We also found, using microinjection of specific antagonists, that alpha(2)-adrenoceptors inthis nucleus appear to be activated as a consequence of imidazoline receptor activation. Thus, there appears to be a close relationship between imidazoline receptors and alpha(2)-adrenoceptors located in the RVLM in mediating the hypotension and inhibition of renal sympathetic nerve activity. Furthermore in recent studies using a noradrenergic neurotoxin microinjected into the RVLM we found that this treatment selectively blocked the actions of moxonidine but not clonidine, suggestingthat I-1-imidazoline receptors may be located on adrenergic terminalsin situ. By contrast, clonidine acts predominantly via alpha(2)-adrenoceptors, perhaps located on cell bodies in the nucleus. We conclude that there is indeed a close nexus between 'presynaptic' imidazoline receptors on noradrenergic terminals and 'downstream' alpha(2)-adrenoceptors within the RVLM. Our hypothesis brings together opposing points of view that the mechanism for hypotension must involve either the imidazoline receptor or the alpha(2)-adrenoceptor. Clearly both are important. (C) 1998 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 03:31:26