Fig. 2.

Distributions of NR1 mRNA, NR1 protein, and other proteins in brains of CA3-NR1 KO mice. (A to H) Dark field images of in situ hybridization on parasagittal brain sections with a ³³P-labeled NR1 cRNA probe. The sources of the brains were (A) a 5-week-old male fNR1 control; (B) a 5-week-old male mutant [a littermate of the mouse in (A)]; (C, E, and G) an 18-week-old male fNR1 control; (D, F, and H) an 18-week-old male mutant [a littermate of the mouse in (C), (E), and (G)]. Scale bar, 100 μm. (E and F) The hippocampal regions of (C) and (D), respectively, are enlarged. (G and H) The areas of the facial nerve nuclei are enlarged. In the CA3 pyramidal cell layer of the mutant, the level of NR1 mRNA was normal until 5 weeks of age, started to decline thereafter, and reached the lowest and stable level by 18 weeks of age [arrowheads in (D)]. There was no indication of a reduced NR1 mRNA level in the mutant mice relative to the control littermates in any other brain area throughout the postnatal development. In particular, the levels of NR1 mRNA in the mutants’ dentate gyrus (F), cerebellum (B and D), and the facial nerve nuclei (H) are indistinguishable from those of the control littermates (A, C, E, and G). (F) Arrowheads indicate scattered hybridization signals that are likely derived from CA3 interneurons. (G and H) Arrowheads, the facial nerve nuclei. In (E) to (H), scale bar, 25 μm. (I to N) Immunoperoxidase staining of paraffin sections of brains derived from 18-week-old male mice visualized with 3,3′-diaminobenzidine. The primary antibodies used are specific for NR1 (I to L) and for GluR1 (M and N). The genotypes of the mice are fNR1 (control) (I, K, M), and CA3-NR1 KO (mutant) (J, L, N). Medial parasagittal sections were used for experiments other than those in (K) and (L), for which lateral parasagittal sections were used. In the mutants, NR1-IR was selectively deficient in the dorsal [arrowheads in (J) and (L)], as well as ventral [arrows in (L)] area CA3. Scale bar in (I), 100 μm. (K to P) See scale bar in (K), 50 μm. (O and P) Nissl staining of hippocampal sections derived from an 18-week-old male fNR1 mouse (O) and a male CA3-NR1 KO littermate (P). The mutant exhibited no gross morphological alteration.