Figure 3.

Currents evoked with exogenous GABA were outwardly rectifying. A, Current traces during GABA application (1 μm) at different holding potentials (as indicated). Baselines are adjusted to allow comparison of currents. Note the acceleration of desensitization at hyperpolarized potentials and the slow, continuous activation of currents at +40 mV. B, I–V plot of current from the neuron in A. Currents were measured early during GABA application (near “peak” current at −100 mV; closed circle) and before offset of GABA (“steady state”; open circle). Outward rectification is most pronounced for currents measured near steady state. C, Mean current density (in picoamperes/picofarad) as a function of voltage from five cells studied as in A. D, Rectification ratio for endogenous tonic currents and currents evoked with exogenous GABA. Rectification ratio with exogenous GABA is for steady-state currents. No significant difference in rectification ratio was seen for currents evoked with exogenous GABA and endogenous tonic currents under control conditions (p = 0.38). Rectification ratios of tonic currents with SKF or zero Ca²⁺ were not significantly different from control conditions (p = 0.11 and p = 0.90, respectively). The numbers in parentheses indicate number of cells in this and subsequent figures. Error bars represent SEM.