ABSTRACT
The effect of high-frequency repetitive transcranial magnetic stimulation (rTMS) on potassium-chloride cotransporter-2 (KCC2) protein expression following spinal cord injury (SCI) and the action mechanism were investigated.SCI models were established in SD rats.Five groups were set up randomly:normal control group,SCI 7-day (7D) model group,SCI 14-day (14D) model group,SCI-7D rTMS group and SCI-14D rTMS group (n=5 each).The rats in SCI rTMS groups were treated with 10 Hz rTMS from 8th day and 15th day after SCI respectively,once every day,5 days every week,a total of 4 weeks.After the model establishment,motor recovery and spasticity alleviation were evaluated with BBB scale once a week till the end of treatment.Finally,different parts of tissues were dissected out for detection of variations of KCC2 protein using Western blotting and polymerase chain reaction (PCR) technique.The results showed that the BBS scores after treatment were significantly higher in SCI-7D rTMS group than in SCI-14D rTMS group (P＜0.05).As compared with normal control groups,The KCC2 protein in SCI model groups was down-regulated after SCI,and the decrease was much more significant in SCI-14D model group than in SCI-7D group (P＜0.05).As compared with SCI model groups,KCC2 protein in rTMS groups was up-regulated after the treatment (P＜0.05).The up-regulation of KCC2 protein content and expression was more obvious in SCI-7D rTMS group than in SCI-14D rTMS group (P＜0.05).It was concluded that 10 Hz rTMS can alleviate spasticity in rats with SCI,which might be attributed to the up-regulation of KCC2 protein.It was also suggested that the high-frequency rTMS treatment after SCI at early stage might achieve more satisfactory curative effectiveness.
ABSTRACT
The effects of magnetic stimulation on spinal cord injury-induced migration of white matter astrocytes were studied using an established animal model. Ethidium bromide was injected into the dorsal spinal cord funiculus of adult Sprague-Dawley rats on the left side at T10-11. Animals then received 1.52 Tesla-pulsed magnetic stimulation for 5 min at different frequencies (0-20 Hz) for 14 consecutive days. Selected animals received the non-competitive MEK1/2 inhibitor U0126 (10 μM), prior to stimulation at 10 Hz. Lesion volumes were measured in hematoxylin/eosin-stained sections. Expression of glial fibrillary acidic protein (GFAP), microtubule associated protein-2 (MAP-2) and extra-cellular signal-regulated kinase1/2 (ERK1/2) near the epicenter of injury was examined by Western blotting with quantification using an image analysis system. Lesion volumes decreased and GFAP and p-ERK1/2 expression increased with increasing magnetic stimulation frequency (0-10 Hz). MAP-2 expression was not affected at any frequency. Pretreatment with U0126 reduced GFAP and ERK1/2 expression and increased lesion volumes in response to stimulation at 10 Hz. It is concluded that magnetic stimulation increases the migration of astrocytes to spinal cord lesions. Activation of the ERK1/2 signaling pathway is proposed to mediate astrocyte migration and glial scar formation in response to spinal cord injury.