Brain distribution and molecular cloning of the bovine GABA ρ1 receptor

GABAC receptors were originally found in the mammalian retina and recent evidence shows that they are also expressed in several areas of the brain, including caudate nucleus, brain stem, pons and corpus callosum. In this study, plasma membranes from the caudate nucleus were microinjected into X. laevis oocytes. This led the oocyte plasma membrane to incorporate functional bicuculline-resistant, Cl− conducting bovine GABA receptors, similar to those of the retina. Immunolocalization of the GABA ρ1 subunit revealed its expression in bovine neurons in the head of the caudate as well as in the olive, cuneiform and reticular nuclei of the brain stem. The same antibodies failed to show expression in the callosum and pons, where the GABA ρ1 mRNA was previously detected.The cloned GABA ρ1 sequence predicts a protein with 473 amino acids and 74–93% similarity to other GABA ρ1 subunits. Oocytes injected with the cDNA express a non-desensitizing, homomeric receptor with a GABA EC50 = 6.0 μM and a Hill coefficient of 1.8.The results confirm the presence of GABAC receptor mRNAs in several areas of the mammalian brain and show that some of these areas express functional GABA ρ1 receptors that have the classic GABAC receptor characteristics.