Beneficial effects of early environmental enrichment on motor development and spinal cord plasticity in a rat model of cerebral palsy

Abstract

Cerebral palsy (CP) results from nonprogressive lesions in the immature brain generating changes on the neuromuscular system. Environmental enrichment (EE) is a combination of stimuli that provides greater motivation and interest in novel movement exploration through the provision of various devices associated to enhanced social stimulation that would mimic the physiotherapy approach. The aim of this study was to verify whether EE is able to prevent the establishment of motor impairment in a CP rat model. The animals were divided in two groups: control animals (healthy) and animals submitted to a CP model. After this, the pups were exposed to two environments: enriched or standard, totaling four groups: Control group (without CP in a standard environment), CP group (CP model in a standard environment), EE group (without CP in an enriched environment) and CP–EE (CP model in an enriched environment). The experimental model was induced in pregnant Wistar rats by the association of maternal exposure to bacterial endotoxin, perinatal anoxia and sensorimotor restriction of the pups. The assessment of motor skills was held using the following tests: open field, rotarod, horizontal ladder, narrow suspended bar and stride length. The histological analysis evaluated the mean cross-sectional area (CSA) of the soleus muscle fibers, the mean CSA of motoneuronal somata and expression of synaptophysin in the ventral horn of the spinal cord. EE was able to prevent the motor deficits, however, it did not reverse the muscle atrophy observed in CP animals. Furthermore, there was an average increase in the mean area of motoneurons and an increase in the expression of synaptophysin in the ventral horn of the spinal cord of the CP–EE group in relation to CP animals reared in a standard environment. Hereupon, the stimulus increment provided by EE can prevent the onset of motor deficits and histological changes in a CP rat model.