Figure 8.
Activity-dependent plasticity of VGLUT1 expression and glutamate release. A, Double immunostaining for VGLUT1 and the vesicle protein synapsin I after 48 h of incubation with either BIC to block GABAA receptors and increase neuronal activity or AP-5 to block NMDA receptors and decrease neuronal calcium flux. B, Mean VGLUT1 expression (VGLUT1 IOD normalized by synapsin I IOD at the same synapse) was reduced following chronic GABAA receptor blockade (*p = 0.02; unpaired t test; values scaled to control) and enhanced by chronic NMDA receptor blockade (***p < 0.001; unpaired t test; values scaled to control). C, Comparison of EPSC amplitude attenuation by 600 μm γ-DGG in control, BIC, and AP-5-treated cultures. Each data point represents an average of three adjacent sampled EPSCs (0.2 Hz). Representative pre-DGG and post-DGG baselines, normalized to their respective predrug levels for comparison, are shown. D, Typical attenuation of control, BIC, and AP-5-treated EPSCs by 600 μm γ-DGG in the paired connection exhibiting median attenuation for the group. Traces are EPSCs averaged from multiple samples of a single connection, normalized by predrug amplitudes for direct comparison. E, Summary data of γ-DGG attenuation across multiple connections: BIC-treated transmission is significantly more at tenuated than nontreated control transmission (*p < 0.05; unpaired t test; values scaled to control). AP-5-treated transmission is significantly less attenuated than nontreated control transmission (p < 0.01; unpaired t test; values scaled to control). F, γ-DGG attenuation measured in mEPSCs as an additional control. BIC-treated transmission is significantly more attenuated by γ-DGG application than nontreated control mEPSCs (*p < 0.05; unpaired t test), indicating that observed changes in glutamate release correspond to differences in per vesicle glutamate release. G, Sample mEPSCs from bicuculline-treated, control, or AP-5-treated cultures. Calibration: 15 pA, 150 ms.H, Mean mEPSC amplitude is significantly reduced in BIC-treated cultures compared with nontreated control cultures and is significantly elevated in AP-5-treated cultures (*p < 0.05; unpaired t test). CTRL, Control; Syn I, synapsin I.