DIFFERENTIAL-EFFECTS OF TRITON X-100 ON LIGAND-BINDING TO GABA(B) RECEPTORS IN MOUSE CEREBRAL-CORTEX, CEREBELLUM AND WHOLE-BRAIN

1. Pretreatment of whole brain membranes with Triton X-100 (0.01-0.05 v/v%) increased the specific binding of [H-3]baclofen without change o f non-specific binding. Although the treatment increased the affinity of all the GABA(B) agonists tested, that of antagonists either tend to be decreased or unchanged. Furthermore, the treatment potentiated Gpp (NH)p-induced inhibition of [H-3]baclofen binding. 2. Affinity for [H- 3]baclofen in the cerebral cortex was increased following Triton X-100 (0.02 v/v%) treatment, whereas binding characteristics in the cerebel lum were not significantly changed. 3. These results suggest that the properties of cerebellar and cerebral cortical GABA(B) receptors diffe r from each other, and that pretreatment with Triton X-100 not only af fects agonist and antagonist binding to GABA(B) receptors differential ly, but also changes the coupling between GABA(B) receptors and guanin e nucleotide regulatory proteins.