Clerc N, Furness J B, Bornstein J C, Kunze W A
Department of Physiology, University of Melbourne, Parkville, Victoria, Australia.
Neuroscience. 1998 Feb;82(3):899-914. doi: 10.1016/s0306-4522(97)00318-7.
Intracellular recording, dye filling and immunohistochemistry were used to investigate neurons of the proximal duodenum of the guinea-pig. Recordings were made from neurons of the myenteric plexus in the presence of nicardipine to quell muscle contractions, using microelectrodes that contained the marker substance Neurobiotin. Preparations were subsequently processed histochemically to reveal nerve cell shapes and immunoreactivity for calbindin, calretinin or nitric oxide synthase. Neurons were distinguished by their shapes and axonal projections as Dogiel type II, Dogiel type I, filamentous descending interneurons and small filamentous neurons. Dogiel type II cells had large cell bodies and multiple axon processes. They each had a broad action potential (mean half-width, 2.9 ms) and a prominent inflection (hump) on the falling phase of the action potential. The majority (70%) of Dogiel type II cells were AH neurons, defined by their having a prolonged hyperpolarizing potential that followed a soma action potential and lasted more than 2 s. Fast excitatory postsynaptic potentials were not recorded from Dogiel type II neurons. Two thirds of Dogiel type II neurons fired phasically in response to intracellularly injected 500 ms depolarizing current pulses and one-third fired tonically. Calbindin immunoreactivity occurred in 70% of Dogiel type II neurons. Dogiel type I neurons had lamellar dendrites and a single axon. They had brief action potentials (mean half-width, 1.7 ms) with no, or a slight hump. They responded to fibre tract stimulation with fast excitatory postsynaptic potentials. Only 2/21 exhibited a prolonged hyperpolarization following action potentials. The majority of Dogiel type I neurons thus belong to the S neuron category. Nine Dogiel type I neurons fired phasically in response to 500 ms depolarizing current pulses, while 12 fired tonically. Filamentous descending interneurons had long, branching filamentous dendrites and a single anally-projecting axon which gave rise to varicose branches in myenteric ganglia. Action potential characteristics of filamentous interneurons ranged between those of Dogiel type II and type I neurons. Small neurons. Small neurons with short filamentous, or few simple dendrites were also characterized. They had single axons, which could be traced either locally to the circular muscle, or to the longitudinal muscle. None of 12 filamentous interneurons or of 10 small filamentous neurons exhibited a prolonged post-spike hyperpolarization, whereas fast excitatory postsynaptic potentials were recorded from a majority. It is concluded that the morphological types of neuron that are encountered in the ileum also occur in the duodenum, but the electrophysiological characteristics of the neurons are more variable for each morphological class. Thus, it is not always possible to predict the morphology of myenteric neurons in the duodenum from their electrophysiological properties. Part of the electrophysiological variability appears to be due to duodenal neurons being more excitable than ileal neurons.
采用细胞内记录、染料填充和免疫组织化学方法研究豚鼠近端十二指肠的神经元。在尼卡地平存在的情况下，使用含有标记物质Neurobiotin的微电极，从肌间神经丛的神经元进行记录，以抑制肌肉收缩。随后对标本进行组织化学处理，以显示神经细胞的形态以及钙结合蛋白、钙视网膜蛋白或一氧化氮合酶的免疫反应性。根据神经元的形态和轴突投射，将其区分为多极（Dogiel II型）、双极（Dogiel I型）、丝状下行中间神经元和小丝状神经元。Dogiel II型细胞具有大的细胞体和多个轴突分支。它们各自具有宽的动作电位（平均半宽度为2.9毫秒），并且在动作电位的下降相上有一个明显的转折（驼峰）。大多数（70%）的Dogiel II型细胞是AH神经元，其定义为在胞体动作电位之后具有持续时间超过2秒的延长的超极化电位。未从Dogiel II型神经元记录到快速兴奋性突触后电位。三分之二的Dogiel II型神经元在细胞内注入500毫秒去极化电流脉冲时呈相位性放电，三分之一呈紧张性放电。70%的Dogiel II型神经元有钙结合蛋白免疫反应性。Dogiel I型神经元具有层状树突和单个轴突。它们具有短暂的动作电位（平均半宽度为1.7毫秒），没有或只有轻微的驼峰。它们对纤维束刺激产生快速兴奋性突触后电位。只有2/21在动作电位后表现出延长的超极化。因此，大多数Dogiel I型神经元属于S神经元类别。9个Dogiel I型神经元在500毫秒去极化电流脉冲刺激下呈相位性放电，而12个呈紧张性放电。丝状下行中间神经元具有长的、分支的丝状树突和单个向肛门投射的轴突，该轴突在肌间神经节产生曲张分支。丝状中间神经元的动作电位特征介于Dogiel II型和I型神经元之间。小神经元。还对具有短丝状或很少简单树突的小神经元进行了特征描述。它们具有单个轴突，可局部追踪至环形肌或纵行肌。12个丝状中间神经元或10个小丝状神经元中均未表现出动作电位后的延长超极化，而大多数记录到了快速兴奋性突触后电位。得出的结论是，在回肠中遇到的神经元形态类型在十二指肠中也存在，但每种形态类别的神经元的电生理特征更具变异性。因此，根据十二指肠肌间神经元的电生理特性并不总是能够预测其形态。电生理变异性的部分原因似乎是十二指肠神经元比回肠神经元更易兴奋。
