Figure 5.

Expression profiles of NMDA-receptor isoforms in the lumbar spinal cord from trained and untrained type 2 SMA-like mice. a–c, An important decrease in the NR2A subunit expression level is observed in the lumbar spinal cord of the type 2 SMA-like mice at 12 d of age at the level of the transcripts compared with controls (a) whereas the expression of either the NR3B (b) or the NR1 (c) subunit genes remains unchanged. The exercise regimen proves to specifically enhance the NR2A subunit gene expression in SMA-like as well as in control mice. Scale bars: 50 μm for all images, except 250 μm for the large views of the spinal cord. d, The quantification of NR2A transcripts in the spinal cord at 12 d of age by real-time RT-PCR further substantiates the assumption of an exercise-induced reactivation of the NR2A gene expression in trained SMA-like mice (n = 3; *p < 0.05). e, The immunodetection level of NR2A in motor neurons, identified for their immunoreactivity for ChAT, is in agreement with the in situ hybridization data. The low NR2A labeling in motor neurons from untrained type 2 SMA-like mice is to be compared with the high detection of this protein in the motor neurons of trained SMA-like mice, at 12 d of age. Scale bars, 50 μm. f, In contrast, no difference in the NR1 distribution in the spinal cord of SMA-like and control mice could be evidenced (n = 4).