An homogeneous population of beta 1-adrenoceptors subserves inhibitory responses in guinea-pig ileal preparations.

In transmurally stimulated guinea-pig ileal preparations, the pA2 values obtained with the selective beta 1- and beta 2-adrenoceptor antagonists atenolol and ICI 118,551 were independent of the beta-adrenoceptor agonist used [-)-isoprenaline or fenoterol) and were similar to values reported in isolated cardiac tissue. On the basis of these results, the relaxant responses to beta-adrenoceptor agonists in guinea-pig ileal preparations appear to be mediated by an homogeneous population of beta 1-adrenoceptors.