Autoradiographic characterisation of beta-adrenoceptors in chick brain using [3H]CGP 12177

An autoradiographic method for labelling beta(1)- and beta(2)-adrenoceptors using [3H]CGP 12177 as a radioligand is described as well as the procedure for an autoradiographic saturation kinetic study. The method afforded higher quality autoradiographs as well as an improvement in the tissue preservation when assayed in birds and chick embryos. The results confirmed the K(d) values previously reported for membrane homogenate binding. The use of different radioligands to characterise beta-adrenoceptors, the higher B(max) values found with autoradiography than those obtained by the membrane homogenate binding method and the typical errors in quantifying autoradiography are discussed. It is concluded that the method described here considerably improves autoradiographic beta-adrenergic characterisation.