Figure 4.

Type III Nrg1 heterozygous mice have decreased spine densities within proximal regions of apical dendrites of hippocampal pyramidal neurons compared with that of wild-type littermates. A, Diagram of a section (bregma, 3.40–3.64) containing the ventral subiculum (diagonal crossed lines) and a representative coronal section (Golgi stain) from which the pyramidal neurons were chosen (dashed line) and analyzed. Scale bar, 800 μm. B, Two wild-type neurons (+/+) and two heterozygous neurons (+/−) traced by Neurolucida program and reconstructed as three-dimensional structures are shown here as two-dimensional. Scale bar, 100 μm. C, Montages of photomicrographs of apical dendrites of a pyramidal neuron from +/+ or +/− animal. The proximal and distal parts of the apical dendrites are indicated (shown here are dendrites 50∼210 μm away from the center of the cell body). There are many more spines (examples indicated by white arrows) on dendrites from +/+ than from +/− mice. Scale bar, 10 μm. D, Spine densities were plotted against increasing shell radius from the center of the soma. The results are from 30 neurons of five +/+ (shown in blue) and 44 neurons of five +/− (shown in red) animals. Heterozygous mice have significantly lower spine densities at the 50–200 shell radius compared with +/+ animals (nonparametric Kolmogorov–Smirnov test; *p_genotype < 0.05 and **p_genotype < 0.01, respectively). Error bars indicate SEM.