Figure 5.

Properties of free-subunit receptors. (A and B) Representative examples of DS2 potentiation in oocytes injected with α4 +β2 +δ or with α4 +β2 free subunits. The ratios of RNA amounts were 5:1:5 and 5:1, respectively (see Supporting InformationFigure 1). GABA (0.3 µM) responses were potentiated by DS2 (1 µM) in oocytes injected with δ subunit RNA but not in oocytes injected with α4 +β2 alone. (C) Summary of oocytes challenged as in A and B (n= 8 and 10 respectively). *P < 0.05, significantly different from α4 +β2 +δ; two-tailed unpaired t-test. (D) Demonstration of stronger efficacy of THIP (1 mM) compared with 30 µM GABA on both classes of receptor (n= 8 and 10 respectively). (E) Zn²⁺ sensitivity of δ-lacking receptors was higher (n= 8 and 10 respectively, 1 µM GABA, 1 µM Zn²⁺). *P < 0.05, significantly different from α4 +β2 +δ; two-tailed unpaired t-test (F) Furosemide sensitivity at both classes of receptor was higher than observed on synaptic-like receptors (cf. Figure 3), but sensitivity to furosemide was higher on δ subunit-containing receptors (n= 7 and 10). *P < 0.05, significantly different from α4 +β2 +δ; two-tailed unpaired t-test.