Figure 3.

The effects of taurine on synaptic versus extrasynaptic GABA_A receptors. A, A typical recording of sIPSCs in a VB neuron in the presence of 50 μm taurine. Strychnine (1 μm) was present throughout so as to exclude the contribution of glycine receptors (as well as recordings in Figs. 4 and 6). Averaged sIPSC traces (>100 events per ensemble trace) before (black) and after (gray) taurine application; superimposed traces illustrate the similarity in amplitude and decay time. B, The normalized amplitude (0.97 ± 0.06), decay time constant (1.03 ± 0.03), and frequency (1.03 ± 0.09) of sIPSCs after 50 μm taurine perfusion. These parameters are not significantly different from those obtained under control conditions (p > 0.05; n = 11). C, A representative current trace demonstrating that in the presence of 50 μm taurine, 500 nm midazolam did not shift the baseline current. D, In a different neuron than in C, ZnCl₂ (20 μm) partially blocked the taurine-induced outward current as evidenced by the small (∼20 pA) shift in the current baseline. E, In a different neuron than in C and D, gabazine (10 μm) effectively blocked the taurine-induced outward current as well as all sIPSCs. The shift in the current baseline is ∼60 pA. F, Averaged current shifts produced by gabazine (n = 7), Zn²⁺ (n = 6), and midazolam (n = 7) after taurine application. Error bars represent SE.