title: ERK is involved in the reorganization of somatosensory cortical maps in adult rats submitted to hindlimb unloading.
abstract: Sensorimotor restriction by a 14-day period of hindlimb unloading (HU) in the adult rat induces a reorganization of topographic maps and receptive fields. However, the underlying mechanisms are still unclear. Interest was turned towards a possible implication of intracellular MAPK signaling pathway since Extracellular-signal-Regulated Kinase 1/2 (ERK1/2) is known to play a significant role in the control of synaptic plasticity. In order to better understand the mechanisms underlying cortical plasticity in adult rats submitted to a sensorimotor restriction, we analyzed the time-course of ERK1/2 activation by immunoblot and of cortical reorganization by electrophysiological recordings, on rats submitted to hindlimb unloading over four weeks. Immunohistochemistry analysis provided evidence that ERK1/2 phosphorylation was increased in layer III neurons of the somatosensory cortex. This increase was transient, and parallel to the changes in hindpaw cortical map area (layer IV). By contrast, receptive fields were progressively enlarged from 7 to 28 days of hindlimb unloading. To determine whether ERK1/2 was involved in cortical remapping, we administered a specific ERK1/2 inhibitor (PD-98059) through osmotic mini-pump in rats hindlimb unloaded for 14 days. Results demonstrate that focal inhibition of ERK1/2 pathway prevents cortical reorganization, but had no effect on receptive fields. These results suggest that ERK1/2 plays a role in the induction of cortical plasticity during hindlimb unloading.
authors.affiliation: Université Lille Nord de France, Lille, France. erwan.dupont@univ-lille1.fr
authors.forename: Erwan
authors.initials: E
authors.lastname: Dupont
authors.forename: Laurence
authors.initials: L
authors.lastname: Stevens
authors.forename: Laetitia
authors.initials: L
authors.lastname: Cochon
authors.forename: Maurice
authors.initials: M
authors.lastname: Falempin
authors.forename: Bruno
authors.initials: B
authors.lastname: Bastide
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Canu
mesh_terms: D000375:Aging / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D019417:Hindlimb Suspension / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013003:Somatosensory Cortex / Q000187:drug effects / Q000201:enzymology*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D005419:Flavonoids; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one