Parvalbumin-positive interneurons are selectively reduced in Clstn2−/− mice. (a, b) Parvalbumin (PV) punctate immunofluorescence was reduced in hippocampal regions of Clstn2−/− mice (sp, stratum pyramidale). Two-way RM ANOVA, genotype effect F(1,6)=20.0, P=0.0042 and **P<0.01 by Bonferroni post hoc test comparing with WT. Scale bar, 20 μm. (c) Sample immunofluorescence in hippocampal CA1 and cortex showing reduced numbers of parvalbumin-positive but not calbindin-positive interneurons in Clstn2−/− as compared with WT mice. Scale bar, 100 μm. (d) The number of parvalbumin-positive interneurons was reduced in multiple brain regions of Clstn2−/− mice. For each region, all laminae were included in the cell counts. For cortex, the primary motor cortex region was analyzed. Two-way RM ANOVA, genotype effect F(1,16)=50.4, P<0.0001 and *P<0.05, **P<0.01, and ***P<0.001 by Bonferroni post hoc test comparing with WT for the same region. (e–g) The numbers of somatostatin, calretinin and calbindin immunopositive interneurons were unaltered in Clstn2−/− mice. Two-way ANOVA, no genotype effect F(1,40)=0.019, P=0.89 (somatostatin), F(1,29)=0.056, P=0.82 (calretinin), F(1,16)=1.03, P=0.33 (calbindin).