Fig. 5.
Modification of α1β3H267Cγ2L γ-aminobutyric acid (GABA) type A (GABAA) receptors with p-chloromercuribenzensulfonate (pCMBS). The panels on the left show examples of voltage clamp current traces during modification under four different conditions. Colored traces are responses to 3 μM GABA, and black traces are responses to 1 mM GABA. Arrows indicate modification exposures, which were followed by 5-min wash. The starred arrows indicate exposure to 1 μM pCMBS for 10 s. The panels on the right show the corresponding initial linear rate analyses for combined normalized response I3μM/I1mM ratios from all oocytes used for each condition. Points represent the ratio of I3μM/I1mM, normalized to the premodification control, and plotted against cumulative pCMBS exposure. Points in the upper right portion of the panel represent response ratios after modification with 1 μM pCMBS. (A) Modification in the absence of GABA. Traces are recorded from one voltage-clamped oocyte expressing α1β3H267Cγ2L GABAA receptors before and after sequential 10-s exposures to 10 nM pCMBS. (B) Initial modification rate analysis for combined data from all oocytes modified with pCMBS alone (n = 5). The line through the first four points has a fitted slope of 1.3 ± 0.19 × 106 M−1 s−1. Maximal normalized response ratio = 5.4 ± 0.25 (n = 5; mean ± SEM). (C) Modification in the presence of GABA. Current responses from a single oocyte during sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA. (D) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA (n = 9). The fitted linear slope is 3.6 ± 0.25 × 106 M−1 s−1. Maximal normalized response ratio = 5.2 ± 0.24 (n = 8; mean ± SEM). (E) Modification in the presence of GABA and propofol. Current responses from one oocyte before and after sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA plus 10 μM propofol (PRO). (F) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA and propofol (n = 5). The fitted linear slope is 3.0 ± 0.47 × 106 M−1 s−1. Maximal normalized response ratio = 5.3 ± 0.27 (n = 5; mean ± SEM). (G) Modification in the presence of GABA and R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid (mTFD-MPAB). Current responses from one oocyte before and after sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA plus 8 μM mTFD-MPAB. (H) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA and MPAB (n = 7). The fitted linear slope is 1.4 ± 0.22 × 106 M−1 s−1. Maximal normalized response ratio = 5.2 ± 0.18 (n = 5; mean ± SEM).

Modification of α1β3H267Cγ2L γ-aminobutyric acid (GABA) type A (GABAA) receptors with p-chloromercuribenzensulfonate (pCMBS). The panels on the left show examples of voltage clamp current traces during modification under four different conditions. Colored traces are responses to 3 μM GABA, and black traces are responses to 1 mM GABA. Arrows indicate modification exposures, which were followed by 5-min wash. The starred arrows indicate exposure to 1 μM pCMBS for 10 s. The panels on the right show the corresponding initial linear rate analyses for combined normalized response I3μM/I1mM ratios from all oocytes used for each condition. Points represent the ratio of I3μM/I1mM, normalized to the premodification control, and plotted against cumulative pCMBS exposure. Points in the upper right portion of the panel represent response ratios after modification with 1 μM pCMBS. (A) Modification in the absence of GABA. Traces are recorded from one voltage-clamped oocyte expressing α1β3H267Cγ2L GABAA receptors before and after sequential 10-s exposures to 10 nM pCMBS. (B) Initial modification rate analysis for combined data from all oocytes modified with pCMBS alone (n = 5). The line through the first four points has a fitted slope of 1.3 ± 0.19 × 106 M−1 s−1. Maximal normalized response ratio = 5.4 ± 0.25 (n = 5; mean ± SEM). (C) Modification in the presence of GABA. Current responses from a single oocyte during sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA. (D) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA (n = 9). The fitted linear slope is 3.6 ± 0.25 × 106 M−1 s−1. Maximal normalized response ratio = 5.2 ± 0.24 (n = 8; mean ± SEM). (E) Modification in the presence of GABA and propofol. Current responses from one oocyte before and after sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA plus 10 μM propofol (PRO). (F) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA and propofol (n = 5). The fitted linear slope is 3.0 ± 0.47 × 106 M−1 s−1. Maximal normalized response ratio = 5.3 ± 0.27 (n = 5; mean ± SEM). (G) Modification in the presence of GABA and R-5-allyl-1-methyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid (mTFD-MPAB). Current responses from one oocyte before and after sequential 10-s exposures to 10 nM pCMBS plus 1 mM GABA plus 8 μM mTFD-MPAB. (H) Initial modification rate analysis for all oocytes modified with pCMBS plus GABA and MPAB (n = 7). The fitted linear slope is 1.4 ± 0.22 × 106 M−1 s−1. Maximal normalized response ratio = 5.2 ± 0.18 (n = 5; mean ± SEM).

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