Bernard V, Laribi O, Levey A I, Bloch B
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541, Laboratoire d'Histologie-Embryologie, Université Victor Ségalen-Bordeaux 2, 33076 Bordeaux cedex, France.
J Neurosci. 1998 Dec 1;18(23):10207-18. doi: 10.1523/JNEUROSCI.18-23-10207.1998.
The purpose of our work was to investigate how the cholinergic environment influences the targeting and the intracellular trafficking of the muscarinic receptor m2 (m2R) in vivo. To address this question, we have used immunohistochemical approaches at light and electron microscopic levels to detect the m2R in control rats and rats treated with muscarinic receptor agonists. In control animals, m2Rs were located mostly at postsynaptic sites at the plasma membrane of perikarya and dendrites of cholinergic and NPY-somatostatin interneurons as autoreceptors and heteroreceptors, respectively. Presynaptic receptors were also detected in boutons. The m2Rs were usually detected at extrasynaptic sites, but they could be found rarely in association with symmetrical synapses, suggesting that the cholinergic transmission mediated by m2R occurs via synaptic and nonsynaptic mechanisms. The stimulation of muscarinic receptors with oxotremorine provoked a dramatic alteration of m2R compartmentalization, including endocytosis with a decrease of the density of m2R at the membrane (-63%) and an increase of those associated with endosomes (+86%) in perikarya. The very strong increase of m2R associated with multivesicular bodies (+732%) suggests that oxotremorine activated degradation. The slight increase in the Golgi apparatus (+26%) suggests that the m2R stimulation had an effect on the maturation of m2R. The substance P receptor located at the membrane of the same neurons was unaffected by oxotremorine. Our data demonstrate that cholinergic stimulation dramatically influences the subcellular distribution of m2R in striatal interneurons in vivo. These events may have key roles in controlling abundance and availability of muscarinic receptors via regulation of receptor endocytosis, degradation, and/or neosynthesis. Further, the control of muscarinic receptor trafficking may influence the activity of striatal interneurons, including neurotransmitter release and/or electric activity.
我们这项工作的目的是研究胆碱能环境如何在体内影响毒蕈碱受体m2（m2R）的靶向作用和细胞内运输。为解决这个问题，我们采用了光镜和电镜水平的免疫组织化学方法，来检测对照大鼠和用毒蕈碱受体激动剂处理的大鼠体内的m2R。在对照动物中，m2R主要位于胆碱能和NPY-生长抑素中间神经元的胞体和树突质膜的突触后位点，分别作为自身受体和异源受体。在轴突终扣中也检测到了突触前受体。m2R通常在突触外位点被检测到，但很少与对称性突触相关，这表明由m2R介导的胆碱能传递是通过突触和非突触机制发生的。用氧化震颤素刺激毒蕈碱受体会引起m2R区室化的显著改变，包括内吞作用，胞体中膜上m2R密度降低（-63%），与内体相关的m2R增加（+86%）。与多囊泡体相关的m2R非常强烈地增加（+732%）表明氧化震颤素激活了降解。高尔基体中轻微增加（+26%）表明m2R刺激对m2R的成熟有影响。位于相同神经元膜上的P物质受体不受氧化震颤素的影响。我们的数据表明，胆碱能刺激在体内显著影响纹状体中间神经元中m2R的亚细胞分布。这些事件可能在通过调节受体内吞、降解和/或新合成来控制毒蕈碱受体的丰度和可用性方面起关键作用。此外，对毒蕈碱受体运输的控制可能会影响纹状体中间神经元的活性，包括神经递质释放和/或电活动。
