Figure 1.

Different fates of axotomized motor neurons in adult rats and mice. A, Thionine staining of hypoglossal motor neurons. The hypoglossal nucleus is indicated shown by the dashed line. Adult C57BL/6 mice showed extensive motor neuron loss after hypoglossal nerve injury, where as adult Wistar rats did not. cc, Central canal; XII, hypoglossal nucleus; cont, contralateral side; ope, operated side; Scale bars: left, 100 μm; right, 50 μm. B, High-power magnification of operated hypoglossal motor neurons in rats and mice 56 d after axotomy. Scale bars, 25 μm. C, Hypoglossal motor neurons were counted in both Wistar rats (open circles) and C57BL/6 mice (filled circles). The percentage ratio of surviving motor neurons on the operated side compared with that on the control side was calculated. Each point shows the mean± SD (n = 8; p < 0.01 compared with the result of Wistar rat; t test). D, Expression of representative survival-associated molecules 7 d after axotomy was examined by in situ hybridization. Arrows indicate an increase in mRNA on the operated side (right side). ERK1, Extracellular signal-regulated kinase 1. E, Expression of p53-dependent transactivated genes 7 d after axotomy. Scale bars: D, E, top, 1.3 mm; bottom, 0.8 mm. F, Proteins extracted from control (c) and operated (o) hypoglossal nuclei of mice 7 d after axotomy were subjected to Western blot analysis using polyclonal anti-Noxa and anti-GAPDH antibodies.