Further evidence of interaction between vasodilator beta 2- and vasoconstrictor alpha 2-adrenoceptor-mediated responses in maintaining vascular tone in anesthetized rats.
J Cardiovasc Pharmacol
; 14(6): 874-80, 1989 Dec.
Article
em En
| MEDLINE
| ID: mdl-2481776
The importance of the interaction of alpha- and beta-adrenoceptors in maintaining vascular tone in rats was studied. This interaction after clenbuterol (CLEN) treatment indicates an important contribution of the circulating epinephrine (EPI) levels. In urethane-anesthetized rats, the beta 2-adrenoceptor antagonist ICI 118.551 was more effective in antagonizing isoproterenol-induced hypotension (mainly beta 2-mediated) than tachycardia (mainly beta 1-mediated). Intravenous (i.v.) administration of the alpha 2-adrenoceptor agonist clonidine (CLO) induced an initial pressor response followed by a more prolonged hypotension and bradycardia. The initial hypertensive effect was potentiated by previous acute administration of ICI 118.551 as well as by the nonselective beta-adrenoceptor antagonist propranolol, but not by metoprolol, a more selective beta 1-blocker. Fourteen days of administration of the beta 2-adrenoceptor agonist CLEN [0.3 mg/kg, subcutaneously (s.c.) twice daily], a treatment that induces desensitization of beta 2-mediated vasodilation, increased the pressor response induced by CLO, an effect that was not observed in pentobarbital-anesthetized rats. In any case, neither beta-blockers nor CLEN treatment affects the hypotension and bradycardia induced by CLO. Mean blood pressure (BP) of CLEN-treated rats was increased under urethane anesthesia but not under pentobarbital anesthesia. Catecholamine levels (principally EPI) were higher in urethane-anesthetized rats. These results provide further evidence of a functional interaction between alpha 2- and beta 2-adrenoceptor-mediated responses in rat vasculature and suggest that vasodilator beta 2-adrenoceptors might contribute to the determination of peripheral vascular tone when circulating EPI is substantially elevated.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Vasoconstrição
/
Vasodilatação
/
Receptores Adrenérgicos alfa
/
Receptores Adrenérgicos beta
/
Músculo Liso Vascular
Limite:
Animals
Idioma:
En
Revista:
J Cardiovasc Pharmacol
Ano de publicação:
1989
Tipo de documento:
Article
País de afiliação:
Argentina
País de publicação:
Estados Unidos