Constitutive activity of N1^7Y/N2 receptors. (A) Continuous activity (30 s) selected from recordings obtained from one receptor with no agonists added (−/−) or no glutamate added and 0.1 mM Gly (−/Gly). (B) Histograms of closed events observed in the corresponding records shown in A; probability distribution function (thick line) and kinetic components (E₁–E₆, thin lines) calculated with a 6C1O model; the concentration-dependent component areas are in red. (C) Kinetic model used to fit the entire sequence of events in each (−/Gly) record; rate constants (s⁻¹) are given as the rounded means for the entire dataset. All states (C, O) represent glycine-bound glutamate-free receptors.