Poulter M O, Singhal R, Brown L A, Krantis A
Laboratory of Molecular Neuropharmacology, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
Neuroscience. 1999;93(3):1159-65. doi: 10.1016/s0306-4522(99)00174-8.
GABAergic neurons occur in the myenteric plexus and submucosa and their innervations of the gut, where GABA stimulates motor neurons, and non-neural cells via "central type" GABA(A) receptors. These receptors occur on half of the neurons in the rat intestine. The GABA(A) receptor is a ligand-gated chloride channel constructed from different subunit families (alpha, beta, gamma, delta, epsilon). In rat these exist as subtypes, alpha1-6, beta1-3, gamma1-3 and delta, defining the clinically relevant pharmacological features of GABA(A) receptors. However, the identity, distribution, and abundance of enteric GABA(A) receptor subunits are unknown. To identify and map the regional expression of GABA(A) receptor subunit messenger RNAs in the enteric nervous system, we assayed enteric RNA from the ileum of Sprague-Dawley rats by reverse transcription-polymerase chain reaction for alpha1-6, beta 1-3, gamma1-3, and delta subunit messenger RNAs. Subunit messenger RNA localization, was probed by in situ hybridization. Reverse transcription-polymerase chain reaction analysis of RNA from myenteric and submucosal nerve layers revealed the expression alpha1, alpha3, beta2, beta3, gamma1 and gamma3 subunit messenger RNAs. Little alpha4 and alpha6 and no alpha2, beta1, gamma2 or delta subunit messenger RNA were detected. In situ hybridization revealed that transcripts for alpha1, alpha3, alpha5 and beta2 subunits occur in both myenteric and submucous ganglia. However, beta3 messenger RNA was found only in myenteric plexus. The gamma1 subunit messenger RNA was also restricted to the cells in the myenteric plexus while gamma3 was found in cells of both nerve layers. In this study of the subunit messenger RNA expression profile of GABA(A) receptors within the enteric nerve layers we show an abundant, diverse and widespread distribution that is unique in comparison to the CNS. The distinctive and heterogeneous distribution of enteric GABA(A) subunits may be important in the integration of neural control of gut function.
γ-氨基丁酸能神经元存在于肌间神经丛和黏膜下层，以及它们对肠道的神经支配中，在这些部位γ-氨基丁酸通过“中枢型”γ-氨基丁酸A（GABA(A)）受体刺激运动神经元和非神经细胞。这些受体存在于大鼠肠道中一半的神经元上。GABA(A)受体是一种由不同亚基家族（α、β、γ、δ、ε）构成的配体门控氯离子通道。在大鼠中，它们以亚型形式存在，即α1-6、β1-3、γ1-3和δ，这些亚型决定了GABA(A)受体的临床相关药理学特征。然而，肠道GABA(A)受体亚基的身份、分布和丰度尚不清楚。为了鉴定和绘制GABA(A)受体亚基信使核糖核酸（mRNA）在肠神经系统中的区域表达，我们通过逆转录-聚合酶链反应检测了来自Sprague-Dawley大鼠回肠的肠道RNA，以检测α1-6、β1-3、γ1-3和δ亚基的mRNA。通过原位杂交探测亚基mRNA的定位。对肌间和黏膜下神经层RNA的逆转录-聚合酶链反应分析显示，α1、α3、β2、β3、γ1和γ3亚基的mRNA有表达。几乎未检测到α4和α6，也未检测到α2、β1、γ2或δ亚基的mRNA。原位杂交显示，α1、α3、α5和β2亚基的转录本存在于肌间和黏膜下神经节中。然而，β3 mRNA仅在肌间神经丛中发现。γ1亚基的mRNA也局限于肌间神经丛中的细胞，而γ3则在两个神经层的细胞中都有发现。在这项对肠神经层内GABA(A)受体亚基mRNA表达谱的研究中，我们显示出其分布丰富、多样且广泛，与中枢神经系统相比具有独特性。肠道GABA(A)亚基独特且异质的分布可能对肠道功能的神经控制整合很重要。
