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.

Limb segment vibration modulates spinal reflex excitability and muscle mRNA expression after spinal cord injury

“…Thus, repeatedly sampling over different times after limb segment vibration may help to gain a better understanding of dynamic changes in gene transcription (Gomez-Pinilla et al, 2004; Ying et al, 2005; Wang et al, 2010; Dupont et al, 2011). Although brain-derived neurotrophin factor (BDNF), nerve growth factor (NGF), neurotrophins-3 (NT-3), and other trophic factors did not show significant increases in expression levels at 3 h after a single short-term limb segmental vibration, it is not known if repeated training bouts would ultimately change the regulation of BDNF or NGF.…”

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

“…These models induce muscle atrophy and changes in bone structure as physiological consequences observed in humans after space flight or bed-rest [2] – [9] . Other physiological changes as synaptic plasticity changes have been described with this model [10] . In cardiovascular functions, rodent head-down tilt simulates cephalic fluid redistribution, hypovolemia, alters baroreflex function, and causes vessels structural as well as functional adaptations [11] – [13] .…”

ERK Pathway Activation Bidirectionally Affects Visual Recognition Memory and Synaptic Plasticity in the Perirhinal Cortex

“…The ERK 1,2 (also called p42/44 mitogen-activated protein kinase) pathway mediates experience-dependent gene transcription and translational processes in neurons and several studies have identified its pivotal role in experience-dependent synaptic plasticity and in LTM consolidation involving cortex, hippocampus, amygdala, or striatum (Brambilla et al, 1997 ; Atkins et al, 1998 ; Blum et al, 1999 ; Mazzucchelli and Brambilla, 2000 ; Schafe et al, 2000 ; Di Cristo et al, 2001 ; Adams and Sweatt, 2002 ; Mazzucchelli et al, 2002 ; Cancedda et al, 2003 ; Kelleher et al, 2004 ; Thomas and Huganir, 2004 ; Doyère et al, 2007 ; Tsokas et al, 2007 ; Cohen-Matsliah et al, 2008 ; Leon et al, 2010 ; Lin et al, 2010 ; Dupont et al, 2011 ).…”