超声-中频电治疗后大鼠脑啡肽水平与其镇痛效应

背景:超声-中频电疗法具有良好的镇痛效果,该镇痛过程是否有脑啡肽等神经化学类物质参与,需对经超声-中频电作用后大鼠的疼痛反应进行定性、定量分析后验证。目的:观察超声-中频电治疗的镇痛作用及其对大鼠脑啡肽水平的影响,探讨其镇痛作用与脑啡肽神经化学物质变化间的相关性。设计:随机分组设计、对照动物实验。单位:中国医科大学附属一院理疗康复科,中国协和医科大学基础医学研究所。材料:实验于2002-06/2003-03在中国协和医科大学基础医学研究所完成。选择健康雌性Wistar大白鼠40只,随机分为4组,甲硫氨酸脑啡肽测定实验组,甲硫氨酸脑啡肽测定对照组,亮氨酸脑啡肽测定实验组,亮氨酸脑啡肽测定对照组,每组10只,其中甲硫氨酸脑啡肽组及亮氨酸脑啡肽组统称为实验组,甲硫氨酸脑啡肽对照组及亮氨酸脑啡肽对照组统称为对照组。方法:①对实验组大鼠进行超声-中频电治疗,频率0.8MHz,采用连脉方式,调制频率100Hz,超声波声强0.9W/cm2;中频电载波频率4kHz,调制频率100Hz,采用连调波型,中频电流为2mA,作用时间为10min。对照组也经同样处理,但超声-中频电治疗仪不开高压,故无能量输出。采用辐射热甩尾法测定大鼠痛觉,用秒表测定大鼠甩尾反应时间(s)并作为痛阈值。②当超声-中频电作用大鼠10min后立即测痛阈,然后断头取其腺垂体(垂体后叶弃去)及丘脑下部组织,按脑啡肽放射免疫测定法测定其甲硫氨酸脑啡肽及亮氨酸脑啡肽含量。主要观察指标:治疗前后痛阈变化,甲硫氨酸脑啡肽和亮氨酸脑啡肽的含量。结果:纳入动物40只,均进入结果分析。①甲硫氨酸脑啡肽测定实验组和亮氨酸脑啡肽测定实验组大鼠痛阈值变化率分别为265.79%和272.90%,两组间比较差异无显著性(P>0.05)。②大鼠经超声-中频电单次作用后,其腺垂体及丘脑下部甲硫氨酸脑啡肽和亮氨酸脑啡肽含量均较治疗前显著升高[腺垂体甲硫氨酸脑啡肽和亮氨酸脑啡肽变化率分别为(300.48±36.21)%,(204.61±68.65)%,丘脑下部甲硫氨酸脑啡肽和亮氨酸脑啡肽变化率分别为(239.80±59.98)%,(205.53±51.62)%,P<0.05]。③经直线回归分析发现大鼠痛阈的变化值与腺垂体甲硫氨酸脑啡肽含量呈正相关(r=0.91,P<0.01),即腺垂体甲硫氨酸脑啡肽的升高值与痛阈的升高值密切相关,当大鼠痛阈值升高100%时,腺垂体甲硫氨酸脑啡肽含量可较对照组升高117.02%。结论:腺垂体甲硫氨酸脑啡肽水平升高可能是超声-中频电疗法发挥镇痛作用的重要机制之一。

Pain-relieving effect of ultrasound-medium frequency electrotherapy and changes of enkephalin in rats

BACKGROUND: Ultrasound-medium frequency electrotherapy has better pain-relieving effect,whether it involves enkephalin and the like neurotransmitter is still not very clear, it is necessary to carry out qualitative and quantitative analysis of the pain response in rats received ultrasound-medium frequency electrotherapy.OBJECTIVE: To investigate the pain-relieving effect of ultrasound-medium frequency electrotherapy and its influence on the enkephalin content in rats, aiming to probe its underlying mechanism and relationship with neurotransmitter enkephalin.DESIGN: Randomly controlled study taking experimental animals as subjects.SETTING: Department of Physiotherapy, First Hospital Affiliated to China Medical University, Institute of Basic Medicine, Peking Union Medical CollegeMATERIALS: This experiment was carried out at the Institute of Basic Medicine, Peking Union Medical College between June 2002 and March 2003. Forty healthy male Wistar rats were adopted and randomized into four groups,namely methionine enkephalin detection experimental group and control group,as well as leucine enkephalin detection experimental group and control group with 10 rats in each group ,amongst which methionine enkephalin experimental group and leucine enkephalin experimental group were generally designed as experimental group ,with the other two group as control group.METHODS: ①Rats ín the experímental group were subjected to ultrasound-medium frequency electrotherapy with frequency of 0.8 MHz in manner of geminal pulse,the modulatìng frequency was 100 Hz and ultrasound intensity of 0.9 W/cm2;the carrier frequency of medium frequency electricity was 4 kHz with modulating frequency of 100 Hz in manner of continuous wave,the electric current of medium frequency was 2 mA and acting time of 10 min. rats in control group received the same dealing,but the higher voltage of ultrasound-medium frequency electrotheprauetic instrument was not used, thereby no energy output was available. tail flick test(TFr) was used to test rat algesthesia,and stopwatch was used to record the time for tail flick(s) that was taken as the value of pain threshold. ②The threshold of pain was tested at 10 minutes instantly after ultrasoundmedium frequency electric stimulation,and then pituitary (removing the posterior pituitary lobe) and hypothalamus were obtained to detect the content of methionine enkephalin and leucine enkephalin by using radioimmuno assay.MAIN OUTCOME MEASURES: The changes of the pain threshold after treatment,the content of methionine enkephalin and leucine enkephalin.RESULTS: Totally 40 rats were enrolled in the experiment and entered in the results analysis. ① The changing rate of pain threshold in two experimental group were 265.79% and 272.90% respectively,the difference was of no statistical significance (P ＞ 0.05). ②After ultrasoundmedium frequency electrotherapy,the content of methionine enkephalin and leucine enkephalin in pituitary and hypothalamus were obviously higher than before treatment [ The changing rate of methionine enkephalin and leucine enkephalin in adenohypophysis was 300.48 ±36.21)% and(204.61±68.65)% , respectively, compared to (239.80±59.98)%and(205.53±51.62)% in hypothalamus, P ＜ 0.05]. ③Linear regression analysis revealed that the variance of the pain threshold was positively correlated with the content of methionine enkephalin in adenohypophysis(r=0.91 ,P ＜ 0.01), suggesting the increment of methionine enkephalin in adenohypophysis was closely connected with the increment of pain threshold,and the level of methionine enkephalin in adenohypophysis would be higher than that in control group by 117.02% when the value of pain threshold increased by100%.CONCLUSION: One of the important mechanisms for the pain-relieving effect of ultrasound-medium frequency electrotherapy might be the increase of methionine enkephalin in adenohypophysis.