Spencer Nick J, Costa Marcello
Visceral Neurophysiology Laboratory, Department of Physiology, College of Medicine and Public Health & Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia.
Visceral Neurophysiology Laboratory, Department of Physiology, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.
Adv Exp Med Biol. 2022;1383:295-306. doi: 10.1007/978-3-031-05843-1_27.
The enteric nervous system (ENS) is required for many cyclical patterns of motor activity along different regions of the gastrointestinal (GI) tract. What has remained mysterious is precisely how many thousands of neurons within the ENS are temporally activated to generate cyclical neurogenic contractions of GI-smooth muscle layers. This has been an especially puzzling conundrum, since the ENS consists of an extensive network of small ganglia, with each ganglion consisting of a heterogeneous population of neurons, with diverse cell soma morphologies, neurochemical and biophysical characteristics, and neural connectivity. Neuronal imaging studies of the mouse large intestine have provided major new insights into how the different classes of myenteric neurons are activated during cyclical neurogenic motor patterns, such as the colonic motor complex (CMC). It has been revealed that during CMCs (in the isolated mouse whole colon), large populations of myenteric neurons, across large spatial fields, coordinate their firing, via bursts of fast synaptic inputs at ~2 Hz. This coordinated firing of many thousands of myenteric neurons synchronously over many rows of interconnected ganglia occurs irrespective of the functional class of neuron. Aborally directed propulsion of content along the mouse colon is due, in large part, to polarity of the enteric circuits including the projections of the intrinsic excitatory and inhibitory motor neurons but still involves the fundamental ~2 Hz rhythmic activity of specific classes of enteric neurons. What remains to be determined are the mechanisms that initiate and terminate the patterned firing of large ensembles of enteric neurons during cyclic activity. This remains an exciting challenge for future studies.
胃肠道（GI）不同区域的许多周期性运动活动都需要肠神经系统（ENS）参与。一直以来令人费解的是，ENS内究竟有数千个神经元如何在时间上被激活，以产生胃肠道平滑肌层的周期性神经源性收缩。这一直是个特别令人困惑的难题，因为ENS由一个广泛的小神经节网络组成，每个神经节都由异质性的神经元群体构成，这些神经元具有不同的细胞体形态、神经化学和生物物理特性以及神经连接。对小鼠大肠的神经元成像研究为不同类型的肌间神经元在周期性神经源性运动模式（如结肠运动复合体，CMC）中如何被激活提供了重要的新见解。研究发现，在CMC期间（在分离的小鼠全结肠中），大量的肌间神经元在大的空间范围内，通过约2Hz的快速突触输入爆发来协调它们的放电。数千个肌间神经元在许多排相互连接的神经节上同步进行这种协调放电，而与神经元的功能类别无关。沿着小鼠结肠向口推进内容物，在很大程度上归因于肠回路的极性，包括内在兴奋性和抑制性运动神经元的投射，但仍然涉及特定类型肠神经元的基本约2Hz节律活动。尚待确定的是在周期性活动期间启动和终止大量肠神经元有模式放电的机制。这仍然是未来研究的一个令人兴奋的挑战。
