Manchanda Rohit, Appukuttan Shailesh, Padmakumar Mithun
Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India.
J Exp Neurosci. 2019 Jan 17;13:1179069518821917. doi: 10.1177/1179069518821917. eCollection 2019.
As in other excitable tissues, two classes of electrical signals are of fundamental importance to the functioning of smooth muscles: junction potentials, which arise from neurotransmission and represent the initiation of excitation (or in some instances inhibition) of the tissue, and spikes or action potentials, which represent the accomplishment of excitation and lead on to contractile activity. Unlike the case in skeletal muscle and in neurons, junction potentials and spikes in smooth muscle have been poorly understood in relation to the electrical properties of the tissue and in terms of their spatiotemporal spread within it. This owes principally to the experimental difficulties involved in making precise electrical recordings from smooth muscles and also to two inherent features of this class of muscle, ie, the syncytial organization of its cells and the distributed innervation they receive, which renders their biophysical analysis problematic. In this review, we outline the development of hypotheses and knowledge on junction potentials and spikes in syncytial smooth muscle, showing how our concepts have frequently undergone radical changes and how recent developments hold promise in unraveling some of the many puzzles that remain. We focus especially on computational models and signal analysis approaches. We take as illustrative examples the smooth muscles of two organs with distinct functional characteristics, the vas deferens and urinary bladder, while also touching on features of electrical functioning in the smooth muscles of other organs.
与其他可兴奋组织一样，两类电信号对平滑肌的功能至关重要：接头电位，它源于神经传递，代表组织兴奋（或在某些情况下抑制）的起始；以及锋电位或动作电位，它代表兴奋的完成并导致收缩活动。与骨骼肌和神经元的情况不同，平滑肌中的接头电位和锋电位在与组织电特性相关以及在其时空传播方面的理解一直很差。这主要归因于从平滑肌进行精确电记录所涉及的实验困难，也归因于这类肌肉的两个固有特征，即其细胞的合胞体组织以及它们所接受的分布式神经支配，这使得对其生物物理分析存在问题。在这篇综述中，我们概述了关于合胞体平滑肌中接头电位和锋电位的假说和知识的发展，展示了我们的概念是如何频繁地经历根本性变化，以及最近的进展如何有望解开仍然存在的许多谜题中的一些。我们特别关注计算模型和信号分析方法。我们以具有不同功能特征的两个器官——输精管和膀胱的平滑肌为例进行说明，同时也涉及其他器官平滑肌电功能的特征。
