Published in:
British Journal of Pharmacology, 117 (1996) 7, Seite 1374-1376
Language:
English
DOI:
10.1111/j.1476-5381.1996.tb15294.x
ISSN:
0007-1188;
1476-5381
Origination:
Footnote:
Description:
The role of β3‐adrenoceptors in human colonic circular smooth muscle was assessed in vitro by use of the β2‐selective antagonist SR 59230A. Isoprenaline, in the presence of the selective β‐adrenoceptor antagonists CGP 20712A (β1) and ICI 118551 (β2), both at 0.1 μ, concentration‐dependently relaxed the preparation (pEC50 = 5.22). This effect was potently and competitively antagonized by SR 59230A with a pA2 of 8.31, while its R,R enantiomer SR 59483A gave an apparent pKB of 6.21. Relaxation was likewise produced by CGP 12177A (pEC50 = 6.05), but not by BRL 37344. Although only one of these β3‐selective agonists was effective, the remarkably high potency of SR 59230A as a stereospecific antagonist of non‐β1 non‐β2 relaxation of human colonic muscle by isoprenaline provides strong functional evidence of β3‐adrenoceptors in that tissue.