Effect of treadmill exercise on Purkinje cell loss and astrocytic reaction in the cerebellum after traumatic brain injury

The cerebellum is one of the brain areas, which is selectively vulnerable to forebrain traumatic brain injuries (TBI). Physical exercise in animals is known to promote cell survival and functional recovery after brain injuries. However, the detailed pathologic and functional alterations by exercise following an indirect cerebellar injury induced by a TBI are largely unknown. We determined the effects of treadmill exercise on survival of Purkinje neurons and on a population of reactive astrocytes in the gyrus of lobules VIII and IX of the cerebellum after TBI. The rats were divided into four groups: the sham-operation group, the sham-operation with exercise group, the TBI-induction group, and the TBI-induction with exercise group. Cell biological changes of Purkinje neurons following indirect cerebellar injury were analyzed by immunohistochemistry. TBI-induced loss of calbindin-stained Purkinje neurons in the posterior region of the cerebellum and TBI also increased formation of reactive astroyctes in both the granular and molecular layers of the cerebellar posterior region. Treadmill exercise for 10 days after TBI increased the number of calbindin-stained Purkinje neurons and suppressed formation of reactive astroyctes. The present study provides the possibility that treadmill exercise may be an important mediator to enhance survival of Purkinje neurons in TBI-induced indirect cerebellar injury.