Regional differences in cannabinoid receptor/G-protein coupling in rat brain

Cannabinoid receptor activation of G-proteins can be mea-sured by WIN 55212–2-stimulated [35S]GTPgS binding. Recep-tor/transducer amplification factors, interpreted as the number of G-proteins activated per occupied receptor, are the ratio of the apparent Bmax of net agonist-stimulated [ 35S]GTPgS bind-ing to the Bmax of receptor binding. The present study exam-ined whether amplification factors for cannabinoid receptors differ among various rat brain regions. In autoradiographic studies with [3H]WIN 55212–2 and WIN 55212–2-stimulated [35S]GTPgS binding, some regions displayed different relative levels of agonist-stimulated [35S]GTPgS binding than receptor binding. To quantify amplification factors, membranes from different brain regions were assayed by saturation bindin