Fig. 2.

Mice with astrocyte-specific knock-out of CaNB1 learned the Barnes maze task, but use serial search strategy. Barnes maze spatial learning test was performed on 2 month-old astrocyte-specific CaNB1 knock-out mice (named as ACN-Ctr and ACN-KO mice) as described elsewhere [55]. The test consisted in one habituation session (180 s) followed by 8 acquisition training sessions (AT sessions) 90 s each during which mice were subjected to a mild intensity stress (loud sound and bright illumination). During AT sessions mice learned location of hidden escape box and the time spent to locate and enter the box (entry latency) was measured. A, performance of ACN-Ctr and ACN-KO mice across training sessions in Barnes maze learning paradigm. A1, no differences were found between entry latency learning curves suggesting that both ACN-Ctr and ACN-KO (statistical analysis was performed using 2-way ANOVA for repeated measures, F(1,18) = 0.45; p = 0.51, n = 10 mice for each genotype). A2, Comparison of search strategies adopted by ACN-Ctr and ACN-KO mice during acquisition trainings (Chi-square (Fisher's exact) test, p = 0.020,, n = 10 mice for each genotype). A3, representative traces of ACN-Ctr (blue) and ACN-KO (orange) mice of the search strategies to locate the escape box. Note that ACN-Ctr prefer direct search, while ACN-KO prefer serial search. Adapted from [55]. B, dorsal hippocampi were harvested either immediately after fist AT session B1 or at the end of the last AT session B2, and were processed for total RNA extraction using TRIzol reagent. First cDNA strand was synthetized from 1 μg total RNA. Real-time quantitative PCR (qPCR) was performed as described elsewhere [55] using specific oligonucleotide primers for C-fos, Arc, Egr1 and Egr2 immediate early genes (IEGs). In ACN-Ctr mice, IEGs were robustly induced both at the beginning and at the end of Barnes maze test. Note higher induction of Egr1 and Egr2 IEGs after the first AT session in ACN-KO mice compared with ACN-Ctr B1. Strikingly, at the end of the last AT session, no induction of IEGs in ACN-KO mice was observed B2. *, p < 0.05 for ACN-Ctr mice exposed to compared with mice which have not been exposed to Barnes maze. #, p < 0.05 and ##, p < 0.01 for ACN-KO mice compared with ACN-KO mice for respective genes (n = 6 mice for each genotype)