Figure 2. Novelty induction of Arc in vivo enhances group 1 mGluR stimulated dendritic Arc translation.

A) Representative image of CA1 neurons from ArcGFP-BAC mice exposed to brief novelty and processed for FISH of Arc mRNA (red) and immunohistochemistry for GFP (green) and β3-tubulin (blue). Dotted outline of ArcGFP+ neuron (filled white arrow) and ArcGFP– neuron (empty arrow) indicates source of dendrites at right. Scale-bar=5 µm. B) Quantification of dendritic Arc mRNA levels in ArcGFP+ neurons (n=48) normalized to that in neighbor ArcGFP– neurons (n=14). C) Representative images of CA1 neurons from ArcGFP-BAC mice exposed to brief novelty and processed for immunohistochemistry of β3-Tubulin (blue), GFP (green) and Arc protein (red). Dotted outline of neurons in left panel indicates the source of dendrites at right. Scale-bar=10 µm D) Quantified group data of Arc/tubulin immunofluorescence in soma or dendrites of ArcGFP+ (n for soma, dendrites- Vehicle; =155,135; DHPG; n=87,77) and ArcGFP– (Vehicle; n=29,19; DHPG; n=22,19) CA1 neurons from vehicle or DHPG-treated acute slices in novelty exposed mice. E) qPCR of Arc mRNA in microdissected CA1 dendritic regions from mice with brief novelty exposure or cage-anesthetized (n = 6 mice/condition) F) Western blot of total Arc immunoprecipitated (upper) and phosphorImager gel scan (lower) of immunoprecipitated, ³⁵S-Met-labeled Arc from Vehicle (Veh) and DHPG-treated hippocampal synaptoneurosomes from cage-anesthetized or novelty-exposed mice. Right: Quantified group data of ³⁵S Met incorporation into Arc immunoprecipitates expressed as a fraction of total immunoprecipitated Arc and normalized to cage-anesthetized+vehicle condition. G) Group average of DHPG (100 µM; 5 min)-induced LTD of extracellularly recorded, evoked field (f)EPSPs (Avg±SEM) in cage-anesthetized (89±3% of baseline; n=10 slices) and novelty-exposed mice (79±2%; n=20), normalized to pre-DHPG baseline. *p<0.05;**p< 0.01; ***p< 0.001; ****p < 0.0001. See also Figure S2.