Cloning and functional expression of the bovine GABAC ρ2 subunit

In this study, using RT-PCR, we found that the ρ1 and ρ2 subunits are widely expressed in the CNS including areas where they have not been previously described such as the bulb, pons and the caudate nucleus. To determine if the GABAC component of the GABA-currents elicited by oocytes expressing cerebellum mRNA was caused by activation of homomeric GABA ρ2 receptors, we cloned the corresponding cDNA and expressed it in Xenopus oocytes. It was found that oocytes injected with ρ2 cDNA, efficiently formed GABA-gated homooligomeric receptors. The GABA-dose-current response gave an EC50 = 1.19 μM and the currents were resistant to bicuculline and reversibly antagonized by the specific GABAC receptor antagonist TPMPA. Altogether, our results indicate a widespread distribution of both ρ1 and ρ2 subunits in the bovine CNS and show further that the ρ2 subunit cDNA isolated from cerebellum, forms fully functional receptors when expressed in Xenopus oocytes.