FIGURE 3.

Activation of intracellular, but not cell surface mGluR5, up-regulates immediate early gene Arc. A, DIV17–18 striatal neurons were treated with the indicated drugs for 3 h before staining for Arc (green) and mGluR5 (red). Quis but not DHPG increased Arc expression in mGluR5-positive cell bodies and neurites. MPEP (10 μm) but not LY393053 (20 μm) abolished Quis-induced Arc levels. B, quantitation of Arc immunofluorescence in neurons (expressed as mean ± S.E., compared with control) in the absence or presence of various ligands treated for indicated times; more than 2500 neurons per treatment condition from 3–6 independent experiments were assessed using High Content Imaging; *, p < 0.05 versus basal level. C, quantitation of Arc staining intensity in mGluR5-positive neurites was measured up to 50 μm from the cell body. Bars represent the mean ± S.E. from at least three independent experiments with more than 140 neurites per treatment condition analyzed. *, p < 0.05; **, p < 0.001 versus basal levels. D, Quis-mediated Arc induction is dependent on transcription and translation. Quantitation of Arc immunofluorescence in neurons (expressed as % of Quis treatment) in the absence or presence of the indicated antagonists (ActD, actinomycin D, transcription inhibitor, 40 μm; CHX, cycloheximide, translation inhibitor, 80 μm) treated for 1 h; ∼700 neurons per treatment condition from n = 4 independent experiments. **, p < 0.001 versus Quis. E, Quis but not DHPG induced Arc+ nuclear puncta. Bars represent mean ± S.E. from three independent experiments: >200 neurons were analyzed per treatment. **, p < 0.05.