Figure 4. Picrotoxin-sensitivity of GABA_CR currents.

A, Example GABA_CR responses evoked by local application of L-glutamate (glu; 100 µM, 10 ms) to activate reciprocal amacrine cell synapses, and their inhibition by picrotoxin. Three individual responses (grey) and the mean response (black) are shown for each condition. B, An example experiment showing inhibition of the tonic GABA_CR current by the same concentrations of picrotoxin, following potentiation of the current by NO-711 (3 µM). C, Example average GABA_CR-mediated mIPSCs during baseline and following application of NO-711 (3 µM), with mean data for average mIPSC charge under these conditions (n = 4). GABA_CR mIPSCs were recorded in Ca²⁺-free extracellular solution to facilitate their detection, in the presence of bicuculline. D, Dose-response curves for picrotoxin inhibition of glu-evoked (n = 4–6) and tonic (n = 3–6) GABA_CR currents, fit with Hill equations to give IC₅₀ values.