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Failure of enhancement by labetalol of bronchopulmonary effects of histamine in guinea‐pigs: independence of α‐adrenoceptor antagonism
Author(s) -
Clerici Christine,
Harf Alain,
MacquinMavier Isabelle
Publication year - 1987
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1987.tb11241.x
Subject(s) - bronchoconstriction , labetalol , propranolol , histamine , prazosin , pharmacology , guinea pig , medicine , antagonist , asthma , receptor , blood pressure
1 The effect of labetalol on histamine‐induced bronchoconstriction was studied in anaesthetized guinea‐pigs. Unlike propranolol (1 mg kg −1 ), the same dose of labetalol did not enhance histamine‐induced bronchoconstriction. 2 To determine whether the absence of enhancement of the respiratory effects of histamine by labetalol was due to its α 1 ‐blocking properties or to its partial agonist activity at β 2 ‐adrenoceptors, the effects of propranolol plus prazosin and of propranolol plus labetalol on histamine‐induced bronchoconstriction were examined. In both cases, the bronchoconstrictor effects of histamine were enhanced to the same extent as with propranolol alone. 3 These data support the hypothesis that the non impairment of respiratory mechanics by labetalol is not due to antagonism at α‐adrenoceptors and may be mediated by its partial agonist activity at β 2 ‐adrenoceptors.