Fig. 5.

MTX causes greater direct gating in α₆ than α₁, but greater potentiation in α₁ than α₆-containing receptors. Experimental design and figure representations are analogous to Fig. 4. (A and B) enhancement of submaximal GABA responses by MTX in cells expressing either (A) α₁β₃γ₂ or (B) α₆β₃γ₂ GABA_A receptors. As with PRO, preapplication of MTX often elicited an inward current directly. (C) MTX directly activates an inward current in the absence of applied GABA, shown as a percentage of the maximal GABA response. This direct current is significantly greater at both 1 and 10 μM MTX for the α₆β₃γ₂ receptors (p < 0.05). (D) Enhancement of an EC₁₀ GABA current response by 1 and 10 μM MTX is significantly greater in the α₁β₃γ₂ at 10 μM.