Fig. 3.

Systematic comparison of CX546 effects. The AMPA receptor subunits GluA (A1, A2, or A4) were transiently transfected into HEK293 cells alone or with each of four TARP variants, and CX546 dose-response curves were measured as described in Fig. 2. Values for E_max and EC₅₀ are summarized in Table 1. A, A1 and A1/TARPs at 1 nM [³H]fluorowillardiine. The CX546 effect was small and not significantly altered by the TARPs. B, A2 and A2/TARPs at 4 nM [³H]fluorowillardiine. γ3 and γ8 significantly increased the E_max for CX546 by approximately 30% (p ≤ 0.001). In contrast, γ2 and γ4 caused only a slight increase in efficacy and the difference from A2 alone was not significant. EC₅₀ values were not significantly altered. C, A4 and A4/TARPs at 51 nM [³H]fluorowillardiine. All four TARPs significantly decreased the E_max of CX546, but the changes relative to A4 alone were largest with γ2 and γ4. D, comparison of E_max values for GluA2 and -4. Coexpression with γ2 and γ4 consistently produced a smaller E_max in both subunits compared to coexpression with γ3 and γ8. Statistical significance was determined by ANOVA (see Table 1).