PB induces a complex I_PB concentration–response relationship and tail current kinetics in whole cells. (A) Individual PB-triggered (−60-mV) Cl⁻ currents (I_PB) from a single cell expressing α₁β₂γ_2S receptors over a range of concentrations (top in μM), where downward deflection indicates increasing current. (B, left) Concentration–response amplitude relationships for peak, plateau, and tail I_PB normalized to peak current with 500 μM PB (means ± SEM; five to seven cells). (Inset) Replots 1,000-μM response (•) and identifies plateau and tail current magnitudes. (Right) Peak concentration–response relationship replotted on logarithmic axes showing linear relationship (solid straight line, slope = 1.7) at low concentrations. Linear relationship with slope = 1 (dashed straight line) shown for comparison. (C, top) Tail currents replotted from A, normalized for amplitude, and shifted temporally to align peaks at the indicated concentrations (μM). Straight line denotes baseline. (Bottom) Selected tail currents replotted on semilogarithmic axes to show exponential components (straight lines with fast [τ_F] and slow [τ_S] time constants as indicated) at designated concentrations to show exponential components of tail current deactivation time course. (Left) 250-μM response manifests biexponential relaxation with straight lines marking periods where each exponential component is dominant. (Right) 5,000-μM response shows a quasi-plateau period from tail current peak to point where the time course is accounted by a monoexponential function. Application period was >30 s.