The functional effects of three novel human isoforms, GABAB1k, l, and m.

<p>Inhibitory effects were measured in <i>Xenopus</i> oocytes 5 days after injecting GABAB1a, GABAB2 cDNA and GIRK1, GIRK2 cRNA along with GABAB1k, l, or m cDNA. For vector controls, vectors were injected in the same amounts as used for the isoforms. Isoform and vector injection amounts varied from 0 to 15 times of GABAB1a injection amount. Used GABA concentration was 3 mM, an approximate maximum response concentration. For each batch, individual GIRK currents from isoform injected oocytes were normalized to percentage by the average vector control current. For nonparametric tests, the individual percent values were changed to log₁₀. After one-way ANOVA and Dunnett's tests, one-tailed unpaired Student's t-tests were performed between no isoform injected groups and the isoform injected groups. A. GABAB1k had no inhibitory effect. B. GABAB1l data showed significant differences by ANOVA and Dunnett's tests (p = 0.0058), and caused significantly decreased GIRK currents at 5× and 6× GABAB1l (**p = 0.0014 and *p = 0.0229, respectively). C. ANOVA and Dunnett's tests showed the significant differences of GABAB1m data (p = 0.0040). GABAB1m showed significant decreases at 11× and 12× GABAB1m (***p = 0.0003 and **p = 0.0064, respectively). The numbers of recorded oocytes are shown above the bars by each group. Data are expressed as the mean ± SEM.