Figure 6.

Effects of RGS-insensitive G_oα_A on channel kinetics in response to GABA-B_1b/2 receptor stimulation. (Ai) Examples of current traces recorded from HKIR3.1/3.2/GGB cells transiently transfected with either G_oα_A (Left) or RGSiG_oα_A (Right). Baclofen (100 μM) was applied for 20 s as indicated. (Aii) Mean data obtained from these experiments. Current densities are shown (Left). Current density was measured at −60 mV before (basal), during (peak), and after (wash) application of 100 μM baclofen for 20 s in the HKIR3.1/3.2/GGB cell line transiently expressing either the PTx-resistant G_oα_A or the RGS-insensitive, PTx-resistant G_oα_A (RGSiG_oα_A). Channel activation (Center) and deactivation (Right) kinetics are shown. We saw no significant difference in channel activation between G_oα_A and RGSiG_oα_A (P > 0.05), whereas deactivation via the RGS-insensitive G protein was dramatically slower than G_oα_A (P < 0.001). (B) Summary of data from similar experiments with the HKIR3.1/3.2/A1 cell line and transiently expressing either G_iα₁C351G or RGSiG_iα₁. (Left) Current densities were comparable in both groups, but no significant differences were seen between the PTx-resistant G_iα₁ and RGSiG_iα₁ in terms of channel activation and deactivation. ttp, time to peak.