Résumés disponibles (91) :

MYSOET Julien (EA7369 éq. 01 - Marie-Helene CANU)
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@mail :  marie-helene.canu@univ-lille1.fr      tél. :  0320434204

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Titre de la communication :
Adaptive changes in the somatosensory cortex after a sensorimotor restriction in adult rats. IGF-1, a key regulator of cortical plasticity ?
Auteurs (et leurs adresses) de la communication :
Mysoet J, Dupont E and Canu MH EA 4488 « Activité Physique, Muscle et Santé », IFR 114, Université Lille 1, Sciences et Technologies, F-59650 Villeneuve d\'Ascq, France ; Université Lille Nord de France, F-59000 Lille, France
Résumé de la communication :
In humans, a chronic reduction in neuromuscular activity through prolonged bed-rest, ageing, or even spaceflight, results in impairment in motor performance. Hindlimb unloading (HU) is a rodent model of disuse commonly used to improve our understanding of effects of hypoactivity on the sensorimotor system. This situation is characterized by an elevation of the lower limbs during 14 days. Studies have shown profound abnormalities in the realization of motor tasks after HU, which are the result of a combination of peripheral (muscle atrophy, disruption in proprioceptive and cutaneous input…) and central factors. Indeed, HU induces a reorganization of the somatosensory cortex (shrinkage of the foot representation area, enlargement of the cutaneous receptive fields, increased responsiveness), and an alteration in neurotransmitters or neurotrophins levels and in their associated signaling pathways. However, the mechanisms involved in this plasticity are still unclear.
Recently, the interest was turned toward the role of Insulin-like Growth Factor 1 (IGF-1) in the brain. Studies have demonstrated that IGF-1 has a pleiotrophic action in the adult brain, where it regulates cell survival, synaptic plasticity, neuronal excitability, and cell metabolism. Since IGF-1 level increases after exercise, it has been suggested to be the mediator of benefic effects of exercise on the brain. At the opposite, whether IGF-1 level is affected by HU is unknown. Thus, the first part of our work was to quantify IGF-1 level in blood and brain tissues by ELISA after a period of HU. Our results showed a decrease in IGF-1 level. The activation level of IGF1 receptor in the somatosensory cortex, examined by western blot, was also decreased.
The second part of our study was to determine whether restoring cortical IGF-1 level during HU could prevent the reorganization of the somatosensory cortex. For this purpose, we assessed cortical reorganization by electrophysiological recordings in HU rats which received a chronic infusion of IGF-1 during the whole HU period. We demonstrated that IGF-1 was directly involved in cortical plasticity since this factor prevented the cortical remapping during HU.
Finally, we tried to determine whether IGF-1 infusion had also beneficial effects on the somatosensory function. We evaluated the performance of animals in behavioral tests such as adhesive removal test or paw withdrawal threshold to mechanical stimulation. Our results showed that HU as well as IGF-1 had mild consequences on the somatosensory performance.
In conclusion, IGF-1 seems to be a key-regulator of cortical plasticity induced by a chronic sensorimotor restriction.

MYSOET Julien (EA7369 éq. 01 - Marie-Helene CANU)