Fig. 1. Parvalbumin (PV) and somatostatin (SSN) immunoreactivities in somatosensory cortex and hippocampus of wild-type and cD2^-/- mice. (A,B) PV neurons are especially reduced in superficial cortical layers in cD2^-/-. (C,D) Hematoxylin-counterstained sections show PV interneurons are reduced in the cD2^-/- hippocampus. (E) PV neuron density is reduced in all regions of cD2^-/- cortex (HP>SS1, M1/M2). (F,G) The relative SSN neuron density distribution is similar in WT and cD2^-/- nulls despite cortex thinning. (H,I) The density of SSN-immunolabeled neurons is slightly increased in the hippocampal stratum oriens and dentate of cD2^-/-. (J) The SSN neuron density is unchanged in cD2^-/- mice. (A-D,F-I) 40 µm sections. a, alveus; o, stratum oriens; p, stratum pyramidale; r, stratum radiatum; l-m, lacunosum moleculare layer; dnt, dentate gyrus; HP, hippocampus; SS1(bf), primary somatosensory cortex (barrel field region); M1/M2, primary and secondary motor cortex; WT, wild type. Mean±s.e.m. densities of PV-IR neurons in the null are expressed as percentage of control (WT). n=5-8 per genotype per region; ^*, P<0.02; ^**, P<0.001.