Kinetic analysis of recombinant mammalian α₁ and α₁β glycine receptor channels

To analyze the influence of the β-subunit on the kinetic properties of GlyR channel currents, α¹-subunits and α ₁β-subunits were transiently expressed in HEK 293 cells. A piezo dimorph was used for fast application of glycine to outside-out patches. The rise time of activation was dose dependent for both receptors and decreased with increasing glycine concentrations. Subunit composition had no effect on the time course of activation. Coexpression of α₁- and β-subunits resulted in a significantly lower EC₅₀ and a reduced slope of the dose-response curve of glycine compared with expression of α₁-subunits alone. For both receptor subtypes, the time course of desensitization was concentration dependent. Desensitization was best fitted with a single time constant at 10-30 μM, with two at 0.1 mM, and at saturating concentrations (0.3-3 mM) with three time constants. Desensitization of homomeric α₁-receptor channels was significantly slower than that of α₁β-receptor channels. The time course of current decay after the end of glycine pulses was tested at different pulse durations of 1 mM glycine. It was best fitted with two time constants for both α₁ and α₁β GlyR channels, and increased significantly with increasing pulse duration.