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Titolo:
Effect of chronic clonidine treatment on transmitter release from sympathetic varicosities of the guinea-pig vas deferens
Autore:
Knight, D; Cunnane, TC; Lavidis, NA;
Indirizzi:
Univ Queensland, Dept Physiol & Pharmacol, Sch Biomed Sci, Narcot Res Lab,St Lucia, Qld 4072, Australia Univ Queensland St Lucia Qld Australia 4072 St Lucia, Qld 4072, Australia Univ Oxford, Dept Pharmacol, Oxford OX1 3QT, England Univ Oxford Oxford England OX1 3QT pt Pharmacol, Oxford OX1 3QT, England
Titolo Testata:
BRITISH JOURNAL OF PHARMACOLOGY
fascicolo: 7, volume: 134, anno: 2001,
pagine: 1480 - 1486
SICI:
0007-1188(200112)134:7<1480:EOCCTO>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
EXTERNAL CALCIUM-CONCENTRATION; JUNCTION POTENTIAL AMPLITUDE; LOCUS COERULEUS NEURONS; NERVE-TERMINALS; PROBABILISTIC SECRETION; ALPHA-ADRENOCEPTORS; RECEPTOR AGONISTS; CROSS-TOLERANCE; BRAIN-SLICES; INHIBITION;
Keywords:
acute withdrawal; clonidine; guinea-pig; neurotransmission; sympathetic varicosities; tolerance;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
44
Recensione:
Indirizzi per estratti:
Indirizzo: Lavidis, NA Univ Queensland, Dept Physiol & Pharmacol, Sch Biomed Sci, Narcot Res Lab,St Lucia, Qld 4072, Australia Univ Queensland St Lucia Qld Australia 4072 d 4072, Australia
Citazione:
D. Knight et al., "Effect of chronic clonidine treatment on transmitter release from sympathetic varicosities of the guinea-pig vas deferens", BR J PHARM, 134(7), 2001, pp. 1480-1486

Abstract

1 Previous studies have demonstrated that chronic pre-synaptic inhibition of transmitter release by morphine evokes a counter-adaptive response in the sympathetic nerve terminals that manifests itself as an increase in transmitter release during acute withdrawal. In the present study we examined the possibility that other pre-synaptically acting drugs such as clonidine also evoke a counter-adaptive response in the sympathetic nerve terminals.2 In chronically saline treated (CST) preparations, clonidine (0.5 muM) completely abolished evoked transmitter release from sympathetic varicositiesbathed in an extracellular calcium concentration ([Ca2+](o)) of 2 mM. The inhibitory effect of clonidine was reduced by increasing [Ca2+](o) from 2 to 4 mM and the stimulation frequency from 0.1 to 1 Hz.3 The nerve terminal impulse (NTI) was not affected by concentrations of clonidine that completely abolished evoked transmitter release.4 Sympathetic varicosities developed a tolerance to clonidine (0.5 muM) following 7-9 days of chronic exposure to clonidine.5 Acute withdrawal of preparations following chronic clonidine treatment (CCT) resulted in a significant (P<0.005) enhancement of neurotransmitter release (3.75 times) above control levels observed in CST preparations.6 The present findings demonstrate an enhancement of neurotransmitter release from sympathetic varicosities following acute withdrawal from chronic clonidine treatment.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 27/09/20 alle ore 06:54:26