Figure 5.

Reducing the frequency of vesicular-dependent GABA release abolishes the tonic GABA_AR-mediated conductance in dLGN relay neurons. A, Continuous current record in 1 and 2 mm external Ca²⁺. Note the increase in both the magnitude of the holding current and the frequency of sIPSCs after switching into 2 mm Ca²⁺. Application of 20 μm SR-95531 resulted in a reduction in the holding current back to the same magnitude as that observed in 1 mm Ca²⁺ (indicated by gray dashed line). B, Plot of individual sIPSC peak amplitude (gray circles) during the experiment illustrated in A. Superimposed onto this plot is the mean sIPSC frequency (solid line) calculated from a running average of 20 consecutive sIPSCs. C–E, Plots of mean tonic GABA_AR-mediated conductance against mean sIPSC frequency for dLGN relay neurons (C), vLGN relay neurons (D), and interneurons recorded in both dLGN and vLGN (E).