Early movement restriction affects the acquisition of neurodevelopmental reflexes in rat pups

Overview & Synopsis

Childhood is a period of construction of the organism, during which interactions with the environment and regular physical activity favour the maturation of the neuronal networks. However, some children exhibit a sensorimotor restriction (SMR) because they are bedridden or they suffer from a neurodevelopmental disorder. In order to better understand the emergence of neuromuscular disorders in these children, a model of SMR has been developed in rats, consisting in hindlimb casting from postnatal day (PND) 1 to PND 28. These animals display a prominent motor phenotype that includes muscle weakness, locomotor disturbances, spinal hyperreflexia but also reduced somatosensory and motor map areas and disturbance of the excitation/inhibition balance in the sensorimotor cortex. In the present study, our objective was to determine whether SMR affects the early postnatal ontogenesis. We explored the neuromuscular development through the determination of the age for achievement of the main neurodevelopmental reflexes (hind limb grasping, righting, hind limb placing, cliff avoidance, negative geotaxis), which represent reliable indicators of neurological and behavioral development. We also evaluated the maturation of postural control. Our results demonstrate that SMR induces a several day delay in the acquisition of primitive reflexes and postural control with respect to controls, suggesting an alteration in the maturation of the nervous system. In conclusion, physical activity and interactions with environment seem necessary for the harmonious maturation of organization and functions of the central nervous system.