Roles of mechanosensory ion channels in myenteric intrinsic primary afferent neurons

肠道神经系统是自主神经系统的一个独立分支，在对肠道压迫做出反应的感觉神经元中有自己的自主神经系统。然而，完全包含在肠壁中的完整神经系统的概念仍在建立中，部分依赖于证明肠道中有内在感觉神经元并研究它们的功能特性。与收缩的肠道及其推进反射有关的特别重要的是兴奋性，内在的机械敏感感觉神经元。我们知道，蠕动传播的运动复合体依赖于内在的肌间感觉神经元，因为实验上沉默这些神经元会导致推进抑制、停滞和死亡。尽管许多类型的肌间神经元(和其他类型的细胞)被证明对拉伸或诽谤有反应，但我们发现了一种化学敏感性的肌间固有初级传入神经元，其放电频率受S压迫的调制。此外，我们提供了在IPAN中存在拉伸敏感通道(躯体BK和轴突阳离子通道)的证据，到目前为止，在其他类型的肌间神经元中还没有发现类似的通道。从而为IPAN的机械传感作用的分子基础提供了初步的实验数据。我们的实验旨在系统地研究IPAN中伸展敏感通道的特性，以帮助理解这些感觉神经元将机械信号与其他决定其兴奋性的因素相结合。 拉伸敏感离子通道提供了肠道运动和iPAN如何感知和响应扩张以启动蠕动之间的联系。我们已经独特地记录了肌间IPAN中机械敏感的BK通道的电流，并显示BK开放抑制神经元放电。我们现在计划定量测量BK通道电流，以建立其开启和关闭特性的最佳模型。这将有助于我们理解通道开放的决定因素如何相互作用来影响整个机械敏感电流。我们确定BK通道的开放是否受到细胞内钙离子和胃肠激素的影响，每个因素都被整合到模型中。IPAN不同于脊髓或迷走神经感觉神经元。接受突触输入，为它们的功能谱系增加了另一个维度。突触输入对BK通道的影响也将在实验上确定。 我们的实验间接推断了感觉神经元轴突上的兴奋性拉伸敏感通道。它们在启动感觉神经元放电和蠕动方面极其重要，但它们的身份或反应特征尚未确定。我们将进行刺激反应实验和离子替代实验，以首次确定哪些神经元通道启动蠕动。这项工作将为在神经细胞水平上控制肠道运动的机制提供第一个分子生理学研究，并将扩大对肠道如何对刺激做出反应的理解，而不依赖于中枢或其他自主神经系统。由于与其他感觉系统相比，目前对肠道IPAN机械转导知之甚少，我们的工作将有助于在目前尚不具备的细节水平上增加肠道感觉生理学方面的知识。这项工作将有助于我的实验室处于肌间神经感觉生理学前沿的加拿大肠道感觉神经科学研究。

The enteric nervous system is an independent division of the autonomic nervous system which contains its own in sensory neurons that respond to gut compression. However, the concept of a complete nervous system contained entirely in the wall of the intestine is still being established and relies in part on showing that there are intrinsic sensory neurons in the gut and studying their functional properties. Of particular importance in relation to the contracting gut and its propulsive reflexes is the excitability intrinsic mechanosensitive sensory neurons. We know that peristaltic propagated motor complexes depend on intrinsic myenteric sensory neurons, because experimentally silencing these neurons causes inhibition of propulsion, stasis and death. Although many types of myenteric neurons (and other types of cells) have been shown to respond to stretch or defamation, we have identified a type of chemosensitive myenteric intrinsic primary afferent neuron (IPAN) whose firing rate is modulated by s compression. Moreover, we provide evidence for stretch sensitive channels (somatic BK and axonic cationic channels) in IPANs, and no equivalent has so far been found in other types of myenteric neurons. We have thus provided beginning experimental data for molecular basis for a mechanosensory role for IPANs. Our experiments are designed to systematically study the properties of stretch sensitive channels in IPANs to help understand these sensory neurons integrate mechanical signals with other determinants of their excitability. Stretch sensitive ion channels provide the link between gut movement and how IPANs sense and respond to distension to initiate peristalsis. We have already uniquely recorded currents from mechanosensitive BK channels in myenteric IPANs and shown that BK opening inhibits neuron firing. We now plan to quantitatively measure BK channel currents to make a best fit model of its opening and closing properties. This will help us in understanding how determinants of channel opening interact to influence the overall mechanosensitive current. We establish if BK channel opening is affected by intracellular calcium, gut hormones, with each fact integrated into the model. IPANs, unlike spinal or vagal sensory neurons. Receive synaptic input adding another dimension to their functional repertoire. The effect effects of synaptic input on BK channels will also be determined experimentally. Excitatory stretch sensitive channels on the sensory neuron’s axons have been indirectly inferred from our experiments. These are extremely important in initiating sensory neuron firing and thus peristalsis yet they have not been identified as to their identity or response characteristics. We will perform stimulus-response experiments and ion substitution experiments to identify for the first time which neuronal channels initiate peristalsis. This work will provide the first molecular physiological study of the mechanisms that control of gut motility at the neurone cellular level and will expand the understanding of how the intestine responds to stimuli, independent of the central or other autonomic nervous systems. Because little is presently known about gut IPAN mechanotransduction compared to other sensory systems, our work will help increase knowledge in gut sensory physiology at a level of detail not presently available. This work will benefit Canadian gut sensory neuroscience research in which my laboratory is at the forefront of myenteric neuron sensory physiology.