HISTOLOGICAL INVESTIGATION OF SPINAL-CORD LESIONS IN THE SPINAL HYPEROSTOTIC MOUSE (TWY TWY) - MORPHOLOGICAL-CHANGES IN ANTERIOR HORN CELLSAND IMMUNOREACTIVITY TO NEUROTROPIC FACTORS/

We examined the morphology of spinal accessory motoneurons and immunor eactivity to neurotrophins, brain-derived neurotropic factor (BDNF) an d neurotrophin (NT)-3, as well as the presence of reactive astrocytosi s in 70 tiptoe walking Yoshimura (twy) mice that develop calcification at C1-C2 vertebral level compressing the spinal cord. At the level of compression, the area of neuronal soma and total length of dendrites of wheat germ agglutinin-horseradish peroxidase (WGA-HRP)-labelled acc essory motoneurons in the medial cell pool decreased significantly wit h decrement in motoneuron population, relative to the control. In cont rast, at sites rostral to the compressive lesion, a significant enlarg ement of the neuron soma and dendritic elongation were noted, associat ed with increased motoneuron population and decreased transverse area of the cord at the level of compression. At this site, enhanced BDNF a nd NT-3 immunoreactivities were evident in the anterior horn cells. In mice with a more severe degree of compression, astrocyte-like cells s howing BDNF immunoreactivity became abundant and axons in the anterior column demonstrated a marked NT-3 immunoreactivity. Our results sugge st increased functional activity of anterior horn cells at levels rost ral to the site of compression. We speculate that the presence of BDNF and NT-3 in neurons and astrocyte-like cells is proportionate to the severity of chronic mechanical compression and may contribute to the h eterotropic neuronal reserve and survival.