Figure 3.

Additivity of conductances evoked by GABA and glycine. (A) The peak current evoked by coapplication of 1.0 mM GABA and 3.0 mM glycine at 0 mV (I_{GABA + gly}; shaded bar) does not differ significantly from the expected peak current (I_expected; hatched bar) calculated from the sum of GABA- and glycine-evoked conductances, as described in Results. Error bars denote SEM (n = 11). (B) Example current traces evoked by 1.0 mM GABA (red) and 3.0 mM glycine (green), and coapplication of 1.0 mM GABA and 3.0 mM glycine (black), in a cell with a remaining uncompensated R_s of 2.0 MΩ. The blue curve shows the sum of currents evoked by GABA and glycine separately, and the dashed line indicates the calculated expected peak current. Note that at peak, the current at coapplication matches the sum of responses to each agonist as well as the calculated expected peak current. In cells with higher remaining uncompensated R_s, the current at coapplication may differ from the sum of responses to each agonist, but may still match the expected peak current. Note also that at some time after peak, the current at coapplication (black) is smaller than the sum of responses to each agonist (blue). The latter feature is explained by the model presented in Fig. 8. Currents were recorded in amphotericin-perforated patch mode.