Figure 2.

DR neurons exhibit a large tonic inhibitory conductance mediated by extrasynaptic GlyRs. (a) Representative recordings (V_H=−60 mV) from DR neurons (left), illustrating the outward and inward current induced by 0.5 μM strychnine (STRY, top trace) and 30 μM glycine (GLY, bottom trace), respectively. The corresponding all-points histograms are given to the right of the traces. Note that the exemplar 5-HT neuron illustrated in the top trace exhibits a large tonic conductance as revealed by strychnine, whereas although the neuron illustrated in the bottom trace exhibits an inward current when challenged with 30 μM glycine, the subsequent application of strychnine only returns the holding current to the pre-glycine level, ie, in the absence of added glycine, this particular neuron does not exhibit an endogenous tonic conductance. (b) A graph summarizing the changes in holding current evoked by strychnine (0.5 μM, n=31) and glycine (30 and 100 μM, n=44 and 10, respectively) for the responsive neurons, ie, 62, 90, and 100% for strychnine, glycine 30 μM, and glycine 100 μM challenges, respectively. Error bars indicate SEM. Labels are the same for calibration bars shown in top and bottom traces.