FIGURE 7.

A neuromodulatory receptor antagonist prevents the enhanced c-fos immunostaining observed at distal CA1 following novel object exposure. (A) Pairs of animals were housed in the same home cage for at least 2 days. Then, either saline or clozapine (10 mg/kg) was intraperitoneally injected in each animal. After 4 h, both animals were exposed to either novel objects or novel place, as described in the Figure 1 legend. After 2 h, slices were prepared and stained as previously described. Images shown are from the pyramidal layer of area CA1 of saline-treated and clozapine-treated animals (straightened by ImageJ; scale bar = 100 μm). (B) The number of c-Fos positive cells after novel object exposure was analyzed in area CA1 as described in Figure 1. The total integrated NeuN signals in same areas used for c-Fos expression analysis did not differ between groups (Supporting Information Fig. 7B). The number of c-Fos positive cells at distal CA1 was significantly reduced by clozapine-treatment (P = 0.001 in Wilcoxon rank sum test; n = 6 pairs of animals). (C) The number of c-Fos positive cells after novel place exposure was analyzed in area CA1. The total integrated NeuN signals in same areas used for c-Fos expression analysis did not differ between groups (Supporting Information Fig. 7B). The saline-treated animals displayed differential c-Fos expression between proximal and distal CA1 following novel object or place exposure as observed in Figure 1 (a two-way ANOVA interaction: P = 0.0007; n = 7 pairs of animals for novel place exposure experiments). The number of c-Fos positive cells at distal CA1 did not show a significant decrease with clozapine-treatment (P = 0.14 in Wilcoxon rank sum test). For the comparison of c-Fos expression in distal CA1 after novel object and place exposure, a two-way ANOVA was performed with the two variables, novelty type (object vs. place) and drug treatment (saline vs. clozapine), showing a significant interaction (P = 0.0015).