The effects of P4S on responses to GABA and β-alanine in the a1β2γ2L receptor. (A) Sample current responses to various concentrations of P4S and the combination of 1 mM GABA + 50 µM propofol (PA = 1). All traces are from the same cell. The PA of the peak responses to P4S was calculated through normalization to the response to 1 mM GABA + 50 µM propofol. The plot shows the concentration–response relationships for GABA and P4S. The data points give means ± SD from five cells. The solid line was calculated using the averaged fitting results (EC50 = 33 µM, nHill = 1.01, and Ymax = 0.18). The dashed line gives the PA curve in the presence of GABA reported previously for the α1β2γ2L receptor (Shin et al., 2017). (B) Sample current responses to 2–8 µM GABA in the absence and presence of 100 µM P4S. The coapplication of P4S potentiates low-GABA currents and inhibits high-GABA currents. The PA of the control responses were 0.047 (2 µM GABA), 0.079 (4 µM GABA), 0.22 (6 µM GABA), and 0.35 (8 µM GABA). The plot gives the response ratios as a function of PA,GABA. The experiments were done in the presence of 10, 30, or 100 µM P4S. The lines show linear fits to RR > 1 values. The fitted RR = 1 intercepts are 0.18 ± 0.05 (10 µM P4S), 0.18 ± 0.08 (30 µM P4S), and 0.23 ± 0.08 (100 µM P4S). The inset shows the RR = 1 intercepts at higher resolution. (C) Sample current responses to 0.2 and 1 mM β-alanine (β-Ala) in the absence and presence of 30 µM P4S. Coapplication of P4S potentiates low-β-alanine currents and inhibits high-β-alanine currents. The PA of the control responses were 0.036 (0.2 mM β-alanine) and 0.18 (1 mM β-alanine). The plot gives the response ratios as a function of PA,β-alanine. The line shows linear fit with the RR = 1 intercept at 0.24 ± 0.08. The arrows in panels B and C indicate the value of PA,max (0.18) for P4S estimated from the high-concentration asymptote of the concentration–response curve in panel A.
Figure 2.

The effects of P4S on responses to GABA and β-alanine in the a1β2γ2L receptor. (A) Sample current responses to various concentrations of P4S and the combination of 1 mM GABA + 50 µM propofol (PA = 1). All traces are from the same cell. The PA of the peak responses to P4S was calculated through normalization to the response to 1 mM GABA + 50 µM propofol. The plot shows the concentration–response relationships for GABA and P4S. The data points give means ± SD from five cells. The solid line was calculated using the averaged fitting results (EC50 = 33 µM, nHill = 1.01, and Ymax = 0.18). The dashed line gives the PA curve in the presence of GABA reported previously for the α1β2γ2L receptor (Shin et al., 2017). (B) Sample current responses to 2–8 µM GABA in the absence and presence of 100 µM P4S. The coapplication of P4S potentiates low-GABA currents and inhibits high-GABA currents. The PA of the control responses were 0.047 (2 µM GABA), 0.079 (4 µM GABA), 0.22 (6 µM GABA), and 0.35 (8 µM GABA). The plot gives the response ratios as a function of PA,GABA. The experiments were done in the presence of 10, 30, or 100 µM P4S. The lines show linear fits to RR > 1 values. The fitted RR = 1 intercepts are 0.18 ± 0.05 (10 µM P4S), 0.18 ± 0.08 (30 µM P4S), and 0.23 ± 0.08 (100 µM P4S). The inset shows the RR = 1 intercepts at higher resolution. (C) Sample current responses to 0.2 and 1 mM β-alanine (β-Ala) in the absence and presence of 30 µM P4S. Coapplication of P4S potentiates low-β-alanine currents and inhibits high-β-alanine currents. The PA of the control responses were 0.036 (0.2 mM β-alanine) and 0.18 (1 mM β-alanine). The plot gives the response ratios as a function of PA,β-alanine. The line shows linear fit with the RR = 1 intercept at 0.24 ± 0.08. The arrows in panels B and C indicate the value of PA,max (0.18) for P4S estimated from the high-concentration asymptote of the concentration–response curve in panel A.

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