Phenoxybenzamine-induced inhibition of cirazoline pressor responses in pithed rats pretreated with organic or inorganic calcium entry blocking drugs.
Eur J Pharmacol
; 102(3-4): 535-9, 1984 Jul 20.
Article
em En
| MEDLINE
| ID: mdl-6149135
ABSTRACT
In groups of propranolol-treated pithed rats pretreatment with either verapamil (1 mg/kg i.a., 20 min) or the inorganic calcium entry blocker (CEB), cobalt (23.8 mg/kg i.a., 20 min) reduced maximum obtainable pressor responses to the relatively selective alpha 2-adrenoceptor agonist B-HT 920 (0.1-1000 micrograms/kg i.v.) equally, by approximately 50%. Verapamil and cobalt at these doses had little or no effect upon pressor responses induced by the relatively selective alpha 1-adrenoceptor agonist cirazoline (0.1-1000 micrograms/kg i.v.). Phenoxybenzamine (0.1 mg/kg i.v., 15 min) displaced to the right and reduced by 44% the maximum obtainable pressor responses to cirazoline. Treatment of animals with the combination of either verapamil or cobalt followed by phenoxybenzamine, at the dose levels and pretreatment times given above, produced significantly greater inhibitions of cirazoline pressor responses (83% and 88% reduction in the maximum obtainable pressor responses to cirazoline respectively) than were observed following administration of phenoxybenzamine alone. Since yohimbine (1 mg/kg i.v.) did not significantly affect the residual responses to cirazoline following treatment with phenoxybenzamine the mechanism responsible for this interaction between CEBs and phenoxybenzamine is not mediated via postjunctional alpha 2-adrenoceptors. Additional studies are required to assess the involvement of a possible subtype of alpha 1-adrenoceptors which appear to mediate vascular responses sensitive to CEBs.
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Base de dados:
MEDLINE
Assunto principal:
Fenoxibenzamina
/
Pressão Sanguínea
/
Bloqueadores dos Canais de Cálcio
/
Agonistas Adrenérgicos beta
/
Imidazóis
Limite:
Animals
Idioma:
En
Ano de publicação:
1984
Tipo de documento:
Article