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THE USE OF FUNCTIONAL ANTAGONISM TO DETERMINE WHETHER β‐ADRENOCEPTOR AGONISTS MUST HAVE A LOWER EFFICACY THAN ISOPRENALINE TO BE TRACHEA‐ATRIA SELECTIVE in vitro IN GUINEA‐PIGS
Author(s) -
O'DONNELL STELLA R.,
WANSTALL JANET C.
Publication year - 1977
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.1476-5381.1977.tb07748.x
Subject(s) - isoprenaline , antagonism , guinea pig , pharmacology , in vitro , agonist , medicine , chemistry , endocrinology , receptor , stimulation , biochemistry
1 The relative efficacies of three trachea‐atria selective β‐adrenoceptor agonists, fenoterol, Me 506 and Me 454, compared to isoprenaline, were determined on both trachea and atria of guinea‐pigs. 2 On tracheal preparations the β‐adrenoceptor agonists were used as functional antagonists of carbachol and a comparison of the maximum shifts in the carbachol concentration‐response line produced by each of the β‐adrenoceptor agonists provided a comparison of their efficacies. 3 On atrial preparations carbachol was used as a functional antagonist of the β‐adrenoceptor agonists and comparison of the maximum responses to the β‐adrenoceptor agonists in the presence of carbachol provided a comparison of their efficacies. 4 On trachea and atria the order of efficacy of the compounds was Me 454 > Me 506 ≥ isoprenaline = fenoterol. 5 The results indicated that high efficacy in a non‐catechol β‐adrenoceptor agonist is possible provided there is a favourable N‐substituent group. 6 Since Me 454, Me 506 and fenoterol, which are trachea‐atria selective, have efficacies equal to or greater than that of isoprenaline, which is non‐selective, it is concluded that low efficacy in a compound is not essential for it to show trachea‐atria selectivity in vitro in guinea‐pigs.