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Objective To observe the effects of repeated low and high-frequency transcranial magnetic stimulation (rTMS) on neuropathic pain and the expression of specific activation markers of astrocytes and glial fibrillary acidic protein (GFAP) in the lumbar spinal cord.Methods Twenty-eight male Sprague-Dawley rats were randomly divided into a sham-operated group,a sham-rTMS group,a 1 Hz group and a 20 Hz group,with 7 in each group.The rats in the sham-operated group had their sciatic nerve exposed without ligation,while the other groups underwent sciatic nerve ligation to induce neuropathic pain.Three days after the operation,rTMS was applied to the primary motor cortex (M1) contralateral to the pain once a day for 10 consecutive days.Pain-related behavior and thermal pain response were tested before the operation and before and after the course of rTMS therapy.The expression of GFAP in the lumbar spinal cord was examined.Results All of the rats which underwent sciatic nerve ligation showed pain-related behavior and significantly decreasing thermal pain latency compared with the sham-operated group.After the rTMS therapy the thermal hyperalgia was significantly attenuated in the 20 Hz group but not in the 1 Hz group compared with the sham-rTMS group.The expression of GFAP in the dorsal horn of the lumbar spinal cord ipsilateral to the neuropathic pain was significantly increased in the sham-rTMS group and the 1 Hz group compared with the sham-operated group.Compared with the sham-rTMS group,GFAP levels were significantly lower in the 20 Hz group but not in the 1 Hz group.The pain relief in the 20 Hz group was negatively related to the expression of GFAP.Conclusions Neuropathic pain induced by peripheral nerve injury is associated with increased activity and proliferation of astrocytes in the dorsal horns of the spinal cord.High-frequency rTMS can relieve neuropathic pain through inhibiting the activity and proliferation of astrocytes in the dorsal horns,but low-frequency rTMS has no clinically significant effect.
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Objective In order to explore the mechanism of repetitive transcranial magnetic stimulation rTMS) on neuropathic pain,we observed the effect of different frequencies of rTMS on neuropathic pain and the expression of neuronal nitric oxide synthase (nNOS) in the dorsal root ganglion (DRG).Methods A total of 28 male Sprague-Dawley rats were used and divided into a control group,in which sham-operation was performed,and an experimental group which was further divided into a sham-rTMS group,a 1 Hz group and a 20 Hz group after successful neuropathic pain model was established by operation to ligate the left sciatic nerves,with 7 rats in each group.Three days after the operation,rTMS was applied to the primary motor cortex (M1) contralateral to the pain once dai ly for 10 consecutive days.The pain behavior and nNOS expression in the DRG were measured before and after 10 days of rTMS intervention.Results All the neuropathic pain model rats demonstrated pain-related behaviors 3 days postoperation,the mechanical pain thresholds were significantly lower than those in the control group (P ＜ 0.05).After rTMS treatment,the mechanical hyperalgsia was significantly relieved in 20 Hz group but not 1 Hz group as demonstrated by a comparison with the sham-rTMS group (P ＜ 0.05).The expression of nNOS in DRG ipsilateral to the neuropathic pain was significantly increased in sham-rTMS group and 1 Hz group (P ＜ 0.05) when compared with the control group.Meanwhile,it was shown that expression of nNOS was down-regulated in 20 Hz group but not 1 Hz group (P ＜ 0.05).The degree of pain relief in 20 Hz group was negatively correlated with the expression of nNOS in DRG (P ＜0.05).Conclusions Neuropathic pain induced by peripheral nerve injury is associated with elevated expression of nNOS in the DRG.High-frequency rTMS can relieve neuropathic pain through down-regulating the overexpression of nNOS in the DRG,but the low-frequency rTMS has no such effect.
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Objective To determine normal reference values for conduction in the posterior antebrachial cutaneous nerve.Methods Antidromic sensory conduction examinations of the bilateral posterior antebrachial cutaneous nerve were conducted with fifty-eight healthy subjects.The onset latency,peak latency,peak-to-peak amplitude and conduction velocity of the sensory nerve action potentials (SNAPs) were recorded and the inter-side ratios of the peak-to-peak amplitudes were calculated.Results The observed means (and standard deviations) of the onset time,the peak latency,the amplitude and the conduction velocity were 1.96 (0.12) ms,2.48 (0.14) ms,7.39 (2.36) μV and 61.39 (3.69) m/s,respectively.The side-to-side amplitude ratio (smaller/larger) was 0.88 ± 0.09,and no significant difference was observed between the left and right side.The average peak latency and amplitude were significantly different for different age groups.There was no statistically significant difference among the age groups with regard to onset latency or conduction velocity.Conclusion Conduction in the posterior antebrachial cutaneous nerve is easy to study.The peak latency is prolonged and the amplitude decreases with age,suggesting that different normal reference values should be established for different age groups.
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Objective To characterize the static balance and limits of stability (LOS) of postmenopausal women and evaluate the relationship between bone mineral density (BMD) and balance.Methods Sixty women more than 12 months past menopause and aged 50 to 60 years were included in the study.Group 1 (n =20) consisted of women with normal BMD,group 2 (n =20) women with osteopenia,and group 3 (n =20) women with osteoporosis.The static balance of all the participants was evaluated in upright postural situations for 60 s with the eyes open and with the eyes elosed.Their LOS was quantified using a force platform.Results There was no significant difference in static balance parameters or LOS among the 3 groups.The static balance parameters were not significantly different in either the eyes-open or eyes-closed situation in the osteoporosis and osteopenia groups.The medial and lateral LOS were greater than the anterior and posterior limits in all 3 groups.The anterior LOS was greater than the posterior limits among the women with osteopenia and normal density.Conclusion In postmenopausal women aged 50 to 60 years,BMD did not show any significant association with static balance or LOS.Postmenopausal women had better postural control in the mediolateral than in the anteroposterior direction.In postmenopausal women with osteoporosis,postural control in the anterior direction deteriorates from age 50 to 60.
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Objective To estimate the test-retest reliability of limits of stability (LOS) measurement in healthy young adults. MethodsTwenty-five healthy young adults participated this study.Their center of pressure (COP) displacements were recorded while they stood on a force platform.The subjects performed maximal voluntary sway maneuvers in the anterior,posterior,left and right directions in turn.The LOS in each direction was calculated using balance clinic software.Each subject underwent 3 consecutive,identical tests at 7 day intervals with the same investigator.The test-retest reliability of LOS was analyzed using the intraclass correlation coefficient (ICC).ResultsFor the first test the ICC values ( ICC1 ) of the LOS ranged from 0.790 to 0.857.For the mean LOS of the first two tests the ICC2 ranged from 0.906 to 0.937,and for the mean LOS of three tests the ICC3 ranged from 0.910 to 0.948. ConclusionThe LOS test is a reliable measurement with healthy young adults.In clinical practice,averaging two LOS tests is suggested in assessing balance and postural control with young adults.
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Objective To evaluate the test-retest and inter-rater reliability of the hand-held pressure algometer as a measuring instrument of pressure pain threshold(PPT).Method A total of 37 healthy subjects were recruited for reliability test.Three raters measured the PPT at 12 body sites of the subjects.Each rater conducted three trials on each site.In the validity test,10 patients with active trigger points in the upper trapezius were recruited and measured by one rater using the pressure algometer for PPT,the visual analogue scale(VAS)was also used to evaluate the pain intensity induced by the trigger point.The intraclass correlation coefficient and Spearman correlation coefficient were calculated to reflect the reliability and validity.Results The test-retest and inter-rater reliabilities were both high(ICC＞0.95),with the measurements by one rater were more reliable than measurements by multiple raters.The inter-rater reliability of PPT measurement obtained by using the mean value of 3 trials was higher than any of the 3 trials alone.The PPT values of the trigger points were higher than those of the normal points,and there was a significantly negative correlation between the PPT values of the trigger points and the VAS scores.Conclusion The intra-and inter-rater PPT measurements in healthy subjects obtained with the hand-held pressure algometer were highly reliable.The algometer was valid for quantifying myofascial trigger point sensitivity.