神经蛇毒处理眶下神经对电针镇痛作用的影响

目的:探讨粗纤维在电针"四白"穴对内脏痛的镇痛效应中的作用及其传入途径。方法:SD大鼠36只,随机分为空白组,内脏痛组、电针组、眶下神经切断组,神经蛇毒组及生理盐水组,每组6只。切断大鼠双侧眶下神经以及双侧眶下神经鞘内注射神经蛇毒选择性破坏A类纤维,然后电针双侧"四白"穴,再腹腔注射乙酸造成内脏痛模型,观察大鼠内脏痛的行为学变化(扭体反应)以及孤束核(NTS)和三叉旁核(PTN)的c-fos表达。结果:电针组大鼠扭体次数较内脏痛组明显减少(P0.01),眶下神经切断组大鼠扭体次数较电针组明显增加(P0.01),神经蛇毒组大鼠扭体次数少于内脏痛组(P0.05)。电针组NTS的c-fos表达较内脏痛组明显减少(P0.05),眶下神经切断组较电针组明显增加(P0.01),神经蛇毒组显著低于内脏痛组(P0.05)。电针组PTN的c-fos表达较内脏痛组明显增加(P0.01),眶下神经切断组较电针组明显减弱(P0.01),神经蛇毒组较眶下神经切断组和内脏痛组明显增强(P0.01)。结论:粗纤维不是电针"四白"穴对内脏痛大鼠镇痛效应的主要传入纤维,口面部的躯体感觉传入可能经PTN中继后与内脏的感觉传入在NTS发生汇聚并进行整合,从而产生镇痛作用。

Effect of transection or pretreatment of the infraorbital nerve with snake venom on the analgesia induced by electroacupuncture of "Sibai" (ST 2) acupoint in visceral pain rats

Objective To observe the role of large-diameter fibers of infraorbital nerve (ION) in "Sibai" (ST 2)-electroacupuncture(EA)induced analgesia in visceral pain (VP) rats. Methods A total of 36 SD rats were randomized into control,VP,EA,ION transaction,snake venom(SV) and saline groups,with 6 rats in each group.EA(2 Hz/20 Hz) was applied to bilateral "Sibai" (ST 2) for 20 min.VP model was established by intraperitoneal injection of 0.6% acetic acid(10 mL/kg).Bilateral ION were transacted or pretreated by regional application of snake venom to selectively destroy A fibers,respectively.Behavior reactions were assessed by counting abdominal muscular contractions. Meanwhile,c-fos expression in the nucleus of the solitary tract (NTS) and paratrigeminal nucleus (PTN) was displayed by immunohistochemistry. Results In comparison with control group,the numbers of abdominal muscular contraction,and c-fos immuno-reaction(IR)positive neurons in both NTS and PTN increased significantly in VP group( P<0.001 );while in comparison with VP group,the numbers of the abdominal contraction,and c-fos IR-positive neurons of both NTS and PTN in EA and SV and saline groups decreased considerably( P<0.05 ,P<0.01 ).No significant differences were found between ION transaction and VP groups in the abdominal contraction number,and c-fos IR-positive neurons in both NTS and PTN areas,and among EA and SV and saline groups in the numbers of abdominal contraction and c-fos IR-positive neurons of both NTS and PTN ( P>0.05 ). Conclusion The large-diameter (A) fibers of ION are not the major afferent fibers affecting EA-ST 2 induced analgesia in visceral pain rats;and somatic sensory afferents from orofacial areas and visceral pain input converge in the NTS and PTN,which may be the basis of the EA analgesia in the present study.