Figure 1.

Rescue of presynaptic inhibition by PTX-insensitive Gα_i and Gα_o subunits after PTX pretreatment. (A) Summary of experiments comparing presynaptic inhibition induced by baclofen (50 μM) or adenosine (20 μM) under control conditions, with or without infection with adenoviruses expressing various proteins, and with or without pretreatment with PTX (100 ng ml⁻¹, >24 h). Percent presynaptic inhibition was calculated as the difference between peak EPSC amplitudes under control conditions and in the presence of the drug divided by the control EPSC amplitude, multiplied by 100. Bars represent mean ± SEM, with the number of experiments (n) in parentheses. The experimental conditions (virus and toxin treatment) are indicated below each bar. (B) Traces recorded from a neuron expressing PTX-insensitive Gα_o after pretreatment with PTX. Adenosine (20 μM) or combined application of adenosine and norepinephrine (NE; 10 μM) depressed evoked EPSCs (with a shift toward paired-pulse facilitation), whereas baclofen (50 μM) was without effect. EPSCs were evoked by pairs of 2-ms depolarizing commands (50-ms interpulse interval) every 2 s (arrows). Each trace represents the average of five consecutive recordings; currents evoked by the depolarizing commands are blanked.