Schematic representation of the effect of modified environment and exercise on glial reactivity and motoneurons preservation in the SOD1^G93A mice.

<p>At 90 days of age, sedentary treadmill mice and mice submitted to moderate (10 cm/s) or high exercise (21 cm/s) regimens harbor a marked increase in astrogliosis and a strong microglial reactivity as shown by the presence of high density “packs” of microglia. Conversely, sedentary and 5 cm/s animals show limited astrogliosis and no microglia “packs”. Moreover, modifications observed in the glial compartment correlate with changes in motoneurons survival and morphology. Whereas a dramatic decrease in motoneuron number and size is observed in sedentary mice, exposure to exercise or modified environment induces motoneuron preservation. However, effect on motoneurons preservation depends on the exercise regimen. Indeed, when compared to sedentary treadmill animals, 5 cm/s mice show a preserved number of motoneurons but an altered phenotype and a reduced soma size. On the other hand, 10 and 21 cm/s trained animals present a better preservation of motoneurons number but show an altered phenotype as compared to the sedentary treadmill group.