INFLUENCE OF THE EXERCISE IN THE PLASTICITY OF THE SNC AFTER INJURY: PHYSICAL ACTIVITY MODULATES ASTROCYTIC ACTIVATION AND DENDRITIC ARBORIZATION OF RATS SUBMITTED TO THE ISCHEMIA.

OBJECTIVES: Analyze the influence of the spontaneous physical activity in the processes of astrocytic activation and the disappearance of dendrites of rats submitted to the focal ischemic lesion. METHODS: Male Wistar rats had access to the running wheel for 7 periods of 12 hours before the injury. Sedentary animals stayed in same situations in individual cages without wheel. Exercised (EXE) and some sedentary (SED) rats were submitted to a stereotaxical injection of endotelin-1 (ET-1, 2g) in the left striatum for focal ischemia. Other sedentary rats received injection of solvent (control, CTR). After the surgery, the exercised animals were divided in two groups: interrupted exercise (IEXE, without further access to wheel) and maintained exercise (MEXE, with further access to wheel). After 14 or 30 days of the injury, the animals were sacrificed and their brains processed for of the glial fibrillary acidic protein (GFAP, marker for astrocytes), microtubule associated protein-2 (MAP-2, marker for dendrites). The area of immunoreactivity of the GFAP and MAP-2 around injury and in corresponding area of the contralateral striatum had been quantified by means of the morphometric analysis (KS400, Zeiss). RESULTS: Fourteen days after lesion, bigger area of astrocytic activation around the injury was observed in the CTR (230%, p<0,05), SED (142%,p<0,05) and IEXE (174%, p<0,05) in relation to the contralateral corresponding region. On 30th day after lesion, still it had greater astrocytic activation around the injury in the CTR (87%, p<0,01), SED (128%), IEXE (130%,p<0,05) and now in the MEXE (79%, p<0,05) in relation to the contralateral region. Additionally, the MEXE presented important increase (p<0,001) of the astrocytic activation in the striatum, bilaterally, in relation to the other groups. Reduction on the area of immunoreactivity of the MAP-2 was observed in the lesioned striatum in relation to the contralateral only in the SED (52%, p<0,001) on 14th day. This reduction was observed in the SED (52%, p<0,01), IEXE (63%, p<0,05) and MEXE (34%, p<0,05) on 30th day. The inter-groups analysis, on 14th day, it showed minor area of immunoreactivity of the MAP-2 in the lesioned striatum of the SED in relation to the IEXE (48%,p<0,05) and MEXE (62%, p<0,05). The same analysis on 30th day showed greater area of immunoreactivity of the MAP-2 on MEXE (p<0,01),bilaterally, in relation to the other groups. CONCLUSION: The spontaneous physical activity can modulate astrocytic activation induced to the ischemic injury, as well as reduce the disappearance of dendrites around the injury and promote the increase of the contralateral dendritic arborization. These are some of the responsible mechanisms for the benefits of the exercise in the plasticity of the central nervous system after injury.