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Objective:To compare the effects of repetitive transcranial magnetic stimulation (TMS) at three different relatively high frequencies on neuropathic pain so as to find the best frequency.Methods:One hundred Sprague-Dawley rats were randomly divided into a sham operation group, a model group, a TMS group and a control stimulation group. The TMS group was further divided into a 5Hz group, a 10Hz group, and a 20Hz group. The rats in the model, control stimulation and TMS groups received constriction injury of the sciatic nerve, while the rats in the sham group were given a sham version of the operation. On the third day after the operation the rats in the TMS group and the control stimulation group began to receive TMS treatment. Neuropatic pain was evaluated on the day before the operation, and on the 3rd, 5th, 7th, 10th and 12th days after the operation. The evaluations included the paw withdrawal thermal latency (PWTL) and the paw withdrawal mechanical threshold (PWMT).Results:The average PWTLs and PWMTs in all of the TMS groups increased with the TMS treatment. Those of the 10Hz and 20Hz groups were significantly higher than the 5Hz group′s average, while there were no significant differences between the 10Hz group and 20Hz group.Conclusions:High-frequency TMS at different frequencies has different effects on neuropathic pain, at least in rats. The treatment efficacy at 10 and 20Hz is superior to that at 5Hz.
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Objective:To investigate the effect of paired associative stimulation (PAS) on the recovery of neurological function after cerebral infarction, and to explore whether any such effect is associated with autophagy in the ischemic penumbra.Methods:Sixty adult male Sprague-Dawley rats were randomly divided into a sham operation group ( n=20) and an experimental group ( n=40). The rats of the experimental group underwent 90 minutes of right middle cerebral artery occlusion (MCAO), while the sham group received a sham operation. The experimental group was subsequently divided into a model group ( n=20) and a PAS group ( n=20). The PAS group received 14 days of paired associative stimulation (PAS) beginning 24 hours after the operation. Neurological dysfunction was evaluated with a modified neurological severity scale (mNSS) and the elevated body swing test (EBST) on the 1st, 7th and 14th day after the MCAO. The rats were then euthanized and the expression of LC3Ⅰ, LC3Ⅱ, Beclin1, and Cathepsin B in the ischemic penumbra were detected using Western blotting, while the distribution of LC3 in neurons was detected using double immunofluorescent staining. Results:Compared with the sham group, the average mNSS scores and EBST values of the model and PAS groups were both higher on the 7th and 14th day after the MCAO, with those of the PAS group significantly lower than those of the model group on those days. The average mNSS score on the 14th day was significantly lower than on the 7th day. Compared with the sham group, the average LC3Ⅱ/Ⅰ values, Beclin 1 and Cathepsin B levels of both the model group and the PAS group were significantly higher on the 7th and 14th day after the MCAO, with the LC3Ⅱ/Ⅰ values of the PAS group significantly lower than those of the model group at both time points. The PAS group also had significantly lower Beclin1 and Cathepsin B levels on day 14. On the 7th and 14th days after the MCAO, the average number of LC3-positive cells and the ratio of LC3-positive neurons to total neurons in the model and PAS groups were significantly greater than the those of sham group, with the PAS group′s values significantly lower than those of the model group at each time point.Conclusion:PAS can significantly promote neurological recovery after stroke. The beneficial effects may involve inhibition of neuronal autophagy in the ischemic penumbra.
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Objective@#To observe the effects of paired associative stimulation (PAS) on synaptic ultrastructure, neuron apoptosis and BDNF in rats with cerebral infarct, and explore the possible underlying mechanisms.@*Methods@#Forty-five male Sprague-Dawley rats were randomly divided into three groups: a sham operation group, a model group and a PAS group, with 15 rats in each. All the rats underwent a surgical operation for transient middle cerebral artery occlusion (MCAO) on the right side to model focal cerebral ischemia, with those in the sham operation group left without real occlusion. PAS treatment was given to rats in the PAS group 24h after MCAO model was successfully established, while no special intervention was given to those in the sham operation group and model group. After 28 days of treatment, transmission electron microscopy was used to investigate the ultrastructure of the ischemic penumbra, TUNEL was used to observe the apoptosis of cortex neurons, and real time-PCR to investigate BDNF mRNA expression.@*Results@#It was found that after 28 days treatment: ①The synaptic curvature, the synapse length and the post-synaptic density (PSD) decreased significantly in the rats of model group in contrast to those of the sham control group (P<0.05). And compare to model group, the synaptic curvature, the synapse length and the PSD increased significantly in the rats of PAS group (P<0.05). ②Compare to sham control group, the apoptosis rate of model group and PAS group increased significantly (P<0.05). And the apoptosis rate of PAS group decreased significantly in contrast to those of model group (P<0.05). ③Compare to sham control group, BDNF mRNA expression of the PAS group increased significantly(P<0.05), while BDNF mRNA expression of the model group decreased significantly(P<0.05). BDNF mRNA expression of the PAS group increased significantly in contrast to those of model group (P<0.05).@*Conclusion@#PAS promotes neural plasticity and inhibits apoptosis of cortex neurons of the ischemic penumbra in rats with ischemic cerebral infarction. One of the underlying mechanisms might be related to the up-regulation of BDNF mRNA expression.
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Objective To explore the effects and the underlying mechanisms by which paired associative stimulation ( PAS) of tibial nerve electrostimulation and M1 cortex transcranial magnetic stimulation ( TMS) in pro-moting the recovery of forelimb dysfunction in rats with cerebral ischemic stroke. Methods Resting motor thresholds of left extensor carpi radialis muscle ( ECR) were determined 5 min before and 5 min, 30 min, 60 min after PAS,respectively, in 8 male Sprague-Dawley ( SD) rats. Then 48 male SD rats were divided into a sham group ( n=16) subject to sham surgery, an experimental group (n=32) which was further divided into a MCAO group (n=16) and a PAS group (n=16) after cerebral ischemic stroke model was established successfully by occluding the right middle cerebral artery. 24 hours after surgery, PAS consisting of left tibial nerve stimulation and right M1 cortex area TMS was applied to PAS group once daily for 7 consecutive days. The corner tests and grip strength tests were per-formed before and after 7 days of PAS treatment in each group. The RMTs of left ECR were determined, metabolites of the left area tissue of cervical spinal cord were measured by nuclear magnetic resonance spectrum, and expressions of Bcl-2 and Bax of left and right area tissue of cervical spinal cord enlargement were detected by Western Blot tech-nique after 7 days of intervention. Results The average RMTs of left ECR at 5 min, 30 min, 60 min after PAS were significantly lower than those at 5 min before PAS ( P<0.05) . All rats in experimental group showed significant higher turning scores and lower grip strength when compared with sham group (P<0.001 or P<0.01). After PAS interven-tion, PAS group demonstrated lower turning scores, higher grip strength and lower RMT of left ECR as compared with MCAO group ( P<0.05 or P<0.01) . The expression of GABA of left cervical enlargment was significantly decreased in MCAO group when compared with the sham group ( P<0.05) , and there was no significant difference between MCAO group and PAS group. Meanwhile, other metabolites showed no significant difference among the three groups. The av-erage expression level of Bcl-2 and Bax proteins in both sides of cervical spinal cord enlargment showed no significant difference among three groups either. Conclusions Tibial nerve-M1 cortex area PAS may increase the excitability of motor cortical representation of forelimbs in rats, by which PAS promotes the recovery of forelimb dysfunction in rats with cerebral ischemic stroke.
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Objective To observe the effect of paired associative stimulation ( PAS) on the recovery of sensorimotor function and to explore the mechanism in terms of neural plasticity. Methods Ninety male adult Sprague-Dawley rats were randomly divided into a sham operation group (Sham group), a model group (Model group) and a paired associative stimulation group ( PAS group) , each of 30. Each group was then subdivided into 7-, 14-and 28-day subgroups with 10 rats in each. A model of focal cerebral ischemia and reperfusion was estab-lished using the Longa suture method in the Model and PAS groups. The rats in the Sham group underwent the same surgical procedure except for the occlusion of the middle cerebral artery. The rats received 30 minutes of paired pe-ripheral nerve stimulation and transcranial magnetic stimulation comprising 90 pairs at 0.05 Hz beginning 24 h after the occlusion. The impulse wave width of the peripheral nerve stimulation was 200 μs and the intensity was 6 mA. The intensity of the transcranial magnetic stimulation was 120％ of the resting motor threshold. The other two groups weren't given any intervention. Neurological function was tested using Garcia scores on the 1st, 7th, 14th and 28th day after surgery. The rats were then sacrificed and the expression of MAP-2 and GAP-43 in the ischemic penumbra were detected using western blotting and immunohistochemistry. Results No neurological dysfunction was ob-served in the Sham group at any time. Compared with the Sham group at the same time points, the average Garcia scores of the Model and PAS groups were significantly lower (P≤0.05). However, the average Garcia scores on the 7th, 14th and 28th day were significantly higher in the PAS group compared with the Model group at the same time points ( P≤0.05) . The average Garcia scores of the Model and PAS groups on the 28th day after surgery were significantly higher than those on the 1st day (P≤0.05), but only the PAS group's average Garcia score on the 28th day was significantly higher than that on the 7th day. Compared with the Sham group at the same time points, the expression of MAP-2 and GAP-43 protein in the Model and PAS groups was significantly higher, but with that of the Model group significantly lower than that of the PAS group ( all P≤0.05) . The protein expression of MAP-2 and GAP-43 protein in the PAS group on the 14th day was significantly higher than on the 7th and 28th day ( P≤0.05 for both) . Conclusions PAS can promote the recovery of sensorimotor function after cerebral thrombosis, at least in rats. That may be due to its promoting the expression of the neuroplasticity-associated proteins MAP-2 and GAP-43 in the ischemic penumbra.