Specific binding of [3H]rauwolscine to alpha 2-adrenoceptors in rat cerebral cortex: comparison between crude and synaptosomal plasma membranes.

[3H]Rauwolscine, a specific, potent, radiolabelled alpha 2-antagonist, binds to distinct high- and low-affinity alpha 2-adrenoceptors in crude membrane preparations of the rat cerebral cortex. The concentration of high-affinity alpha 2-adrenoceptors was increased by addition of sodium ions or guanylnucleotides. In synaptosomal plasma membrane preparations, only the low-affinity component was found. Neither sodium or guanylnucleotides caused any increase in the concentration of these low-affinity receptors for [3H]rauwolscine.