NGF促进大鼠膈神经移位迷走神经异化支配心脏的实验研究

EXPERIMENTAL STUDY ON PROMOTION OF SOMATO-VISCERAL HETEROGENIC REINNERVATION WITH NERVE GROWTH FACTOR IN RAT PHRENIC-TO-VAGUS ANASTOMOSIS MODEL

目的探讨NGF对大鼠异化神经(躯体运动神经吻合副交感神经)再生的影响。方法3月龄雄性SD大鼠40只,体重约200g,随机分为3组。A组为对照组(n=10),仅显露左侧膈神经和迷走神经;B、C组为实验组(n=15),将左侧膈神经近端与迷走神经远端进行显微缝合。C组术后腹腔注射NGF(20μg/kg·d),连续3周;A、B组注射等量生理盐水。术后12周电刺激神经检测其支配心脏功能,对再生异化神经进行组织学切片,观察神经再生情况并测定神经轴突通过率和髓鞘厚度。结果电刺激后A、B、C组大鼠尾动脉血压分别下降(20.12±2.57)(、10.63±2.44)(、14.18±2.93)mmHg(1mmHg=0.133kPa),心率分别下降(66.77±9.96)、(33.44±11.82)、(43.27±11.02)次/min。B组大鼠血压、心率下降幅度分别达A组的52.83%、50.08%,C组分别达A组的70.48%、64.80%,C组血压和心率下降幅度均大于B组(P<0.05)。B、C组再生异化神经具有髓鞘结构,轴突均长入迷走神经;B、C组异化神经轴突通过率分别为66.83%±4.46%、81.63%±3.56%,髓鞘厚度分别为(0.25±0.10)、(0.46±0.08)μm,C组异化神经轴突通过率和髓鞘厚度均高于B组(P<0.05)。结论异化神经在性质上属于躯体运动神经;NGF可促进异化神经再生,并提高异化神经的支配效能。

Objective To investigate the influence of nerve growth factor （NGF） on neuroal regeneration of somato-visceral heterogenic reinnervation using a rat phrenic-to-vagus anastomosis model. Methods Forty male SD rats,aging 3 months and weighing 200 g,were selected and randomly divided into 3 groups. In group A （n=10,control group）,phrenic and vagus nerves were exposed and no neurorraphy was performed. In group B （n=15） and group C （n=15）,both nerves were transected and proximal stump of phrenic nevers were microsurgically anastomosed to the distal stump of vagus nerves. Postoperatively,group C was intraperitoneally injected with NGF （20 μg/kg·d）,while groups A and B were given matching saline solution. Twelve weeks later,cardiac function was examined under electrical stimulation of the regenerated nerve. Light and electron microscopies were used to examine the heterogenic regenerated nerve,and the passing rate of axon and thickness of myelin sheath were calculated. ResultsUnder electrical never stimulation in groups A,B,and C,the decreases of blood pressure were （20.12 ± 2.57）,（10.63 ± 2.44）,and （14.18 ± 2.93） mmHg （1 mmHg=0.133 kPa）,respectively; and the decreases of heart rate were （66.77 ± 9.96）,（33.44 ± 11.82）,and （43.27 ± 11.02）/minutes,respectively. In group B,the decrease amplitudes of blood pressure and heart rate were 52.83% and 50.08% of group A,respectively. Blood pressure and heart rate in group C also decreased dramatically; the decrease amplitudes of blood pressure and heart rate in group C were 70.48% and 64.80% of group A. There were significant differences in the decrease amplitudes of blood pressure and heart rate （P〈 0.05） between group B and group C. Morphological observation showed that heterogenic nerve fibers had the structure of matured myelin sheath and their axons could regenerate into the vagus nerve. In group Band group C,the passing rates of axon were 66.83% ± 4.46% and 81.63% ± 3.56%,respectively; and the thicknesses of myelin sheath were （0.25 ± 0.10） μm and （0.46 ± 0.08） μm,respectively; showing significant differences （P 〈0.05） between group B and group C. Conclusion Heterogenic nerve is primarily a somatic motor nerve; NGF can promote the axons of heterogenic nerve to regenerate into the parasympathetic nerve.