Autoradiography of adrenoceptors in rat and human brain: alpha-adrenoceptor and idazoxan binding sites

Abstract

This chapter reviews the current classification of adrenoceptors, and notes the difficulties of combining the molecular biological and pharmacological classifications of adrenoceptors. Possibilities for mapping the distribution of the proposed subtypes of adrenoceptors using currently available ligands are discussed, and the autoradiographic visualisation of the broad subtypes of alpha 1-, alpha 2-, beta 1-, and beta 2-adrenoceptors in the rat, monkey and human brain described and illustrated. The non-selectivity of ligands currently being used to label alpha-adrenoceptors is shown; we compare the distribution of [3H]idazoxan binding sites with the distribution of alpha 2-adrenoceptors visualised using other ligands. Resolution limitations of current autoradiographic approaches are considered and we shown how in situ hybridisation can complement data from receptor labelling studies used to localise receptors to pre- or postsynaptic sites.