Figure 1.

Sensitivity of extrasynaptic-like δ-β2-α4 +β2-α4 receptors to agonists. (A) Responses of a representative oocyte expressing concatemeric δ-β2-α4 +β2-α4 receptors to increasing concentrations of GABA. (B) Responses of a representative oocyte expressing α1 +β2 +γ2L to the same series of GABA concentrations. (C) Summary concentration-response curves for eight oocytes expressing concatemeric receptors and six oocytes expressing α1 +β2 +γ2L subunits. The solid lines represent fits to the Hill equation as described in the Methods. The fits yielded an EC₅₀ of 1.2 µM for concatemeric δ-β2-α4 +β2-α4 receptors and 19 µM for α1 +β2 +γ2L receptors. Hill slopes were also significantly different, as described in the Results. (D) and (E) Representative responses of oocytes expressing the indicated subunit combinations to saturating GABA and THIP. THIP was a full agonist at concatemeric α4/δ-containing receptors but a partial agonist at synaptic-like receptors. (F) and (G) Pentobarbital (Ptb) tail currents exceed responses to GABA in α4/δ-containing concatemeric receptors. The traces are representative responses under the indicated conditions. The duration of agonist presentation is indicated by the horizontal bars.