Auditorium of the CGFB
Defense in french
Title : Impact of motor training on motor spinal network development
My doctoral work is centered around two axes:
Axe 1. Exercise and physical activity are now recognized for their short- or long-term benefits on health and are commonly used in combination with pharmacological treatment to treat several pathologies and to promote functional recovery after trauma. Numerous studies have revealed that dynamic reconfigurations occur in the spinal networks in charge of the locomotor command, when the motor activity is increased or modified. The majority of these data arise from adult rodents. At birth, mouse and rat pups cannot walk due to an immature postural control and exhibit an adult like locomotor pattern around the postnatal day 12 (P15). In the present study, we provide the first investigation of the impact of a swim training performed during the early postnatal development of mice on motor spinal circuits. By combining behavioral, electrophysiological, genomic and biochemical approaches, we show that a transient motor training performed during the two first postnatal days is sufficient to accelerate the maturation of swim pattern in newborn mice, to reshape the transcriptome of motoneurons (MNs) and to alter the synaptic plasticity expressed at reticulospinal synapses as well as some MN intrinsic membrane properties. Moreover, we report that long term effects of the training protocol used could be observed as the monoaminergic spinal contents were increased during the second postnatal week following training. Altogether our data reveal that few changes in the level of activity of the spinal networks could lead to dramatic developmental alterations when performed in the early postnatal life of mouse pups.
Axe 2. Developmentally regulated modulation of lumbar motoneurons by metabotropic glutamate receptors. Metabotropic glutamate receptors (mGluRs) play a major role in the modulation of synaptic transmission and neuronal membrane properties in the central nervous system. In lumbar MNs, the role of mGluRs is largely ignored. Our data show that extensor and flexor MNs exhibit different mGluR expression that is developmentally regulated during the two first postnatal weeks. We performed a detailed electrophysiological analysis of the effects of mGluRs agonists on MN membrane properties and synaptic plasticity as well as their functional impact in behaving animals.
Keywords: Activity-dependent development, Plasticity, Motoneuron, Motor training, Glutamatergic neuromodulation.
Thesis supervisor: Sandrine Bertrand (INCIA)