【作者】 田琴；

【导师】 胡还忠；

【作者基本信息】 华中科技大学 ， 生理学， 2006， 硕士

【摘要】 Jessen等人就证实GABA不仅存在于中枢神经系统,还广泛的分布在胃肠道等外周神经系统中[1]。有研究表明GABA对大鼠,豚鼠,猫和狗等动物消化道平滑肌自主收缩活动产生影响,其作用效果因动物的种类和胃肠的部位不同而不同。产生这种现象的原因可能是GABA的受体分布不同或对非肾上腺能非胆碱能神经作用的缘故,但确切的原因还不十分明确。但GABA在小鼠回肠内的分布及对小鼠平滑肌自主收缩的作用影响的研究尚未见报道。本实验运用免疫组织化学的方法检查了GABA在小鼠回肠的分布;以小鼠回肠肌条收缩幅度变化为指标,观察了GABA对小鼠回肠肌条自主收缩的抑制作用以及一氧化氮合酶（NOS）抑制剂L-NNA,可溶性鸟苷酸环化酶（sGC）抑制剂ODQ,β-受体抑制剂普萘洛尔（Propranolol）对GABA抑制作用的影响。初步讨论了GABA对小鼠回肠自主收缩作用时与NO,cGMP和β-受体的相互关系。实验结果:1.小鼠回肠粘膜层及粘摸下层有GABA阳性细胞和纤维分布;平滑肌肌层可见GABA免疫反应阳性。2.GABA（1×10-6～1×10-3mol/L）抑制了小鼠回肠平滑肌自主收缩幅度。各浓度GABA的幅度与对照组均有统计学差异（P<0.05,n=10）。其中1×10-6 mol/L GABA幅度抑制百分率达（34.7±7.4）%。3.GABAA受体的抑制剂picrotoxin(3×10^-5mol/L)孵育标本后,各浓度的GABA的抑制作用没有改变（P>0.05,n=7）。4. NOS抑制剂L-NNA(1×10-5 mol/L孵育标本后,再加入GABA（1×10-6 mol/L）后,幅度抑制百分率为（15.9±3.8）%,比单独同浓度的GABA的抑制百分率下降,差别有统计学意义（P<0.05, n=6）。5.预先用可溶性鸟苷酸环化酶（sGC）抑制剂ODQ（1×10-6 mol/L）孵育小鼠回肠肌条15min后,再加入GABA（1×10-6 mol/L）,其收缩幅度为（0.34±0.05）g与未加药前自主收缩（0.35±0.05）g幅度相比,没有明显差别（p>0.05,n=5）。与单独加入1×10-6mol/L GABA相比,其抑制百分率由（33.2±7.3）%下降到（4.8±1.3）%,两者相比差异有显著统计学意义（P<0.01,n=5）。6.用L-Arg（5×10-7mol/L）孵育标本15min,1×10-6mol/L GABA幅度抑制百分率仅为（7.1±1.8）%,与单独同浓度的GABA幅度抑制百分率（35.1±7.3）%相比,差异有统计学意义（P<0.01,n=6）。1×10-3mol/L GABA在加入L-Arg后幅度抑制百分率与单独同浓度的GABA幅度抑制百分率相比,差异没有统计学意义（P>0.05,n=6）。7.用propranolol（3×10-6mol/L）孵育标本15min,再加入1×10-6 mol/L GABA,其幅度抑制百分率为（14.6±2.6）%,与单独同浓度的GABA幅度抑制百分率（34.4±7.2）%相比,幅度抑制百分率降低,其差别具有统计学意义（P≤0.01,n=6）。加入propranolol后使1×10-3mol/L GABA的幅度抑制百分率比单独同浓度的GABA的幅度抑制百分率降低,其差异也有统计学意义（p<0.05,n=6）。结论:小鼠回肠有GABA能纤维分布。GABA对小鼠回肠自主收缩主要起抑制作用,这种抑制作用与GABAA受体所介导的Cl-通道无关,而受NO和β-肾上腺素能受体活动的影响。更多还原

【Abstract】 Jessen’s researches confirmed thatγ-aminobutytric acid(GABA) is not only been in the central nervous system, but also been in the peripheral nervous systems such as enteric nervous system. GABA may modulate the gastrointestinal motilities of rat、guinea- pig、dog and cat. Some researches suggest that effect of GABA on the gastrointestinal spontaneous contraction is very complex, depending on the position within the gastrointestinal tract and the animal species studied. The complex actions of GABA maybe relate to the different type receptors of GABA or the interactions between non-adrenergic non-cholinergic neurons and GABA. The exact reasons were not sure. Few reports, however, were founded about distribution of GABA in the alimentary tract and effects of GABA on spontaneous contraction of the smooth muscle in mice.In our experiments, using the immunohistochemical method, the distributions of GABA were explored in the mouse ileum. The contraction changes of the isolated smooth muscle strips were recorded by tension transducer, and the change of the tension was used as the marker to evaluate the effects of GABA. The effects of GABA on the contraction of mouse ileum and the influence of L-NNA, ODQ, propranolol on the action of GABA were analyzed. We also investigated the interactions between GABA and NO,β-receptor.Results:1. The presence of GABA ergic neurons in the myenteric plexus and submucosal neurons were demonstrated in the ileum of mouse.2. GABA inhibited the spontaneous contraction of mouse ileum at the concentrations ranging from 1×10-6 to 1×10-3mol/L(P<0.05,n=10). 1×10-6mol/L GABA decreased the contraction amplitudes by(34.7±7.4)%.3. After incubated the preparations with picrotoxin, GABAA receptor inhibitor, the inhibitory effects on the contraction of mouse ileum caused by GABA have no significant change. (P>0.05,n=7).4. When GABA (1×10-6mol/L) was added in the presence of L-NNA(1×10-5mol/L), inhibition of nitric oxide synthase (NOS), The amplitude inhibitory percent with(15.9±3.8)% was significantly different from amplitude inhibitory percent of single GABA (1×10-6mol/L).(p<0.05,n=6).5. ODQ(1×10-4mol/L) was used to incubate the preparations for 15 min before addition of GABA(1×10-6mol/L). The contraction amplitudes changed from (0.35±0.05)g to (0.34±0.05)g.They did not changed .The percent of the inhibition amplitudes reduced from (33.2±7.3)% to (4.8±1.3)% .They have statistical signification. That is to say, ODQ reduced the inhibitory effects of GABA.6. When the preparations were pre-incubated with L-Arg(5×10-7mol/L), the effect of GABA at the concentration of 1×10-6mol/L was fallen. But the effect of GABA at the concentration of 1×10-3mol/L had no significant change.7. Propranolol (3×10-5mol/L) inhibited the effect of GABA at the concentration of 1×10-6mol/L and 1×10-3mol/L. After the strips were pretreated with propranolol (3×10-6mol/L), the inhibitory percent of contractile amplitude of GABA (1×10-6mol/L) reduced from (34.4±7.2)% to (14.6±2.6) % compared with single GABA(1×10-6mol/L).Conclusion:GABA-ergic fibers distributed in mouse ileum. GABA inhibited the spontaneous contraction of mouse ileac smooth muscle, this inhibitory effect is influenced by NO and the excitation ofβ-receptor. But the effect is independent of the Cl- channel that gated by GABAA receptor.更多还原