Figure 6: In CA2 both PV cell density and PNN intensity are modified after conditioning across genotypes; In CA3, PV cell modification is impaired in Fmr1 KO mice.

A) Example images of a WT naïve coronal slice and (H) an Fmr1 KO naïve slice, with cropped images of CA2 (B; I) and CA3 (E; L). To the right of the cropped images are PV (C; F; J; M) and PNN (D; G; K; N) channels separated. In CA2 there was no genotype difference in PV density (O) or PNN density (P) between WT and Fmr1 KO animals. However PV cell density increased (O) in both naïve and fear conditioned mice across genotypes, among PV cells that are not surrounded by PNN (R). We measured WFA fluorescent intensity in CA2 across genotypes and conditioning. Using this metric we found Fmr1 KO mice have reduced WFA intensity compared to WT mice (S) and a decrease in WFA intensity after conditioning in both genotypes, but no change in PNN density (P; T) or in co-localized PV/PNN cells (Q). In CA3 there was an increase in PV cell density (U) and in PNN cell density (V) in both naïve and fear conditioned mice, which increased the number of co-localized PV/PNN cells (W; fear conditioned only). The increase in PV cells seems to be occurring only in WT mice (U) among PV cells that were not surrounded by PNNs (X). PNNs surrounding non-PV cells showed no change (Y). Conditioning effect #, ##, ###; paired comparison *, **, *** (p = 0.05, 0.01, 0.001). N per group: WT Nv = 5; WT FrC = 6; WT C =7, Fmr1 KO Nv = 6, Fmr1 KO FrC = 6, Fmr1 KO C = 5. Image # per group: WT Nv = 17, WT FrC = 18, WT C = 32, Fmr1 KO Nv = 17, Fmr1 KO FrC = 18, Fmr1 KO C = 25.