脑源性神经营养因子对慢性应激诱导的大鼠结肠高动力的调节作用

Regulatory effects of brain - derived neurotrophic factor on colonic hypermotility induced by chronic stress

目的观察脑源性神经营养因子（BDNF）对慢性应激诱导的大鼠结肠高动力的调节作用。方法建立假避水应激（SWAS）和避水应激（WAS）大鼠模型，取结肠黏膜层检测BDNF和P物质（SP）含量；采用免疫组织化学及Westernblot检测酪氨酸蛋白激酶受体（TrkB）在近端结肠的分布；取近端结肠制备纵行肌（LM）及环形肌（CM）肌条，用张力换能器及多通道生理信号采集处理系统观察BDNF及其受体抗体（TrkB-antibody）对SP诱导的LM和CM收缩活动的影响。结果WAS组黏膜BDNF和SP浓度明显高于对照组[BDNF（6．4±0．3）ng／mg比（3．3±0．2）ng／mg，P〈0．01；SP（661．5±20．6）pg／mg比（250．1±12．1）pg／mg，P〈0．01]；TrkB主要分布于肠神经元及黏膜层，且WAS组肌层TrkB表达显著高于SWAS组（P〈0．01）；BDNF预处理肌条后，WAS组sP诱导的结肠CM收缩显著高于对照组[R值（SP诱导的3min内收缩峰值与基础值的比值定义为R值），8．71±0．90比5．38±0．75，P〈0．05]，且该作用被TrkB—antibody阻断。结论BDNF通过TrkB参与慢性应激诱导的结肠高动力的发生，其受体拮抗剂对应激诱导的肠道动力紊乱有潜在的治疗作用。

Objective To investigate the regulatory effects of brain - derived neurotrophic factor （BDNF） on colonic hypermotility of rats induced by chronic stress. Methods Male Wistar rats were ex- posed to 1 h water avoidance stress （WAS） or sham WAS （SWAS） each day for 10 consecutive days. The serum level of BDNF was determined using enzyme immunoassay kits. Immunohistochemistry and Western blotting were used to assess the expression of the high - affinity receptor of BDNF, and TrkB. The contrac- tions of muscle strips were studied in an organ bath system. Organ bath recordings were used to study the contraction of colonic smooth muscle strips. Results The colonic mucusal concentrations of BDNF and SP were significantly increased in the WAS rats as compared with the SWAS rats [ BDNF ： （6.4 ± 0. 3 ） ng/mg vs. （3.3 ±0.2） ng/mg,SP： （661.5 ±20.6） pg/mg vs. （250. 1 ± 12. 1 ） pg/mg, P 〈0.01 ]. Immuno- histoehemistry revealed the presence of TrkB in the mucosa and myenteric plexus. TrkB was up - regulated in colon devoid of mueosa and submueosa in the stressed rats as compared with the control. Pretreatment of CM strips with BDNF for 10 rain significantly enhanced the amplitude of the SP - induced contractions in WAS rats as compared with the control （ R value, 8. 71 ± 0.90 vs. 5.38 ± 0.75 ,P 〈 0.05 ）, and this effect was reversed by TrkB - antibody. Conelusion BDNF may be involved in the colonic hyperumtility induced by chronic stress via its receptor TrkB, and BDNF receptor antagonistmay has potential clinical therapeutic use in modulating gut motility.