Figure 3

Glial GABA transporter mediated tonic inhibition correlates with network activity. (A) Box-chart representation of the average holding currents from individual experiments during control condition, SNAP-5114 application and washout. Box edges represent 25^th, 50^th and 75^th percentile, open squares represent means, circles connected by lines represent paired individual baseline values. Average holding current in control: [Mg²⁺] = 1,800 μM: 78.9 ± 12.4 pA (N = 12 cells/2 animals); [Mg²⁺] = 100 μM: 63.0 ± 12.0 pA (N = 7 cells/3 animals); [Mg²⁺] = 30 μM: 155.0 ± 12.6 pA (N = 10 cells/3 animals); [Mg²⁺] = 10 μM: 121.2 ± 13.3 pA(N = 8 cells/4 animals); [Mg²⁺] = 1 μM: 88.8 ± 11.8 (N = 15 cells/9 animals); Bottom right: Average change in holding current in response to SNAP-5114 application as a function of the sIPSC frequency. Columns represent the means of holding current changes from all experiments having sIPSC frequency in the given 5 Hz wide frequency range during the control period. (B) Left: Holding currents during exogenous Glu application (100 μM, red) and washout (blue) in [Mg²⁺] = 10 μM buffer in the presence of Glu receptor antagonists CNQX (10 μM) and DL-AP5 (50 μM). Average holding current: 66.2 ± 23.5 pA in control vs. 93.0 ± 27.2 pA in the presence of 100 μM Glu, P < 0.001, N = 15 cells/8 animals. Middle: Holding currents during exogenous Glu application (100 μM, red) and washout (blue) in [Mg²⁺] = 10 μM buffer in the presence of Glu receptor antagonists CNQX (10 μM),DL-AP5 (50 μM) and (S)-MCPG (500 μM). Average holding current: 54.3 ± 17.4 pA in control vs. 69.1 ± 17.1 pA in the presence of 100 μM Glu, P = 0.01, N = 5 cells/4 animals. Right: Average change in holding current in response to increasing concentration (1 μM, 10 μM and 100 μM) of exogenous Glu in the presence of CNQX (10 μM) and DL-AP5 (50 μM). Asterisks represent significant change in holding current (P < 0.05).