Characterization of beta 1- and beta 2-adrenoceptor subtypes in the rat sinoatrial node and stellate ganglia by quantitative autoradiography.

We characterized beta-adrenoceptors in rat sinoatrial node (SA) and stellate ganglia by incubating consecutive tissue sections with [125I]iodocyanopindolol, with or without the beta 1-selective (CGP 20712A) or the beta 2-selective (ICI 118,551) antagonists, followed by quantitative autoradiography. In the stellate ganglia, ICI 118,551 displaced more than 90%, and CGP 20712A less than 5%, of the binding sites. CGP 20712A displaced about 50% of the binding sites in the SA, and about 65% in the rat atria. The SA has a high percentage of beta 2-adrenoceptors and the stellate ganglia contains almost exclusively beta 2-adrenoceptor binding sites, implicating beta 2-adrenoceptors in the control of heart rate in the rat.