LePard K J, Galligan J J
Department of Pharmacology and Toxicology and Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA.
Am J Physiol. 1999 Feb;276(2):G529-38. doi: 10.1152/ajpgi.1999.276.2.G529.
Most fast excitatory postsynaptic potentials (fEPSPs) recorded from guinea pig ileum myenteric plexus are mediated by acetylcholine acting at nicotinic receptors and ATP acting at P2X receptors. These studies examine length and polarity of projection of neurons releasing mediators of fEPSPs. Under ketamine-xylazine anesthesia, animals were sham treated or myenteric pathways were interrupted. After severed axons degenerated, fEPSPs were recorded at the operated site using conventional, intracellular electrophysiological methods and were classified as nicotinic or mixed on the basis of sensitivity to hexamethonium. Cholinergic and noncholinergic fEPSPs were recorded from small, operated segments, suggesting that some neurons have projections between adjacent ganglia. The mean amplitudes of nicotinic and mixed fEPSPs were reduced after circumferential and descending pathways degenerated. The proportion of nicotinic vs. mixed fEPSPs recorded from tissues lacking descending projections was greater than that recorded from sham-treated tissues, suggesting that fibers releasing noncholinergic mediators project aborally. Descending projections communicate with neurons in ganglia at least three rows aboral to their origin. The data suggest that fast noncholinergic neurotransmission could contribute to hexamethonium-resistant descending inhibition during the peristaltic reflex.
从豚鼠回肠肌间神经丛记录到的大多数快速兴奋性突触后电位（fEPSP）是由作用于烟碱受体的乙酰胆碱和作用于P2X受体的ATP介导的。这些研究检测了释放fEPSP介质的神经元投射的长度和极性。在氯胺酮-赛拉嗪麻醉下，对动物进行假处理或中断肌间神经通路。切断的轴突退化后，使用传统的细胞内电生理方法在手术部位记录fEPSP，并根据对六甲铵的敏感性将其分类为烟碱型或混合型。从小的手术节段记录到胆碱能和非胆碱能fEPSP，这表明一些神经元在相邻神经节之间有投射。在环行和下行通路退化后，烟碱型和混合型fEPSP的平均幅度降低。从缺乏下行投射的组织记录到的烟碱型与混合型fEPSP的比例高于假处理组织，这表明释放非胆碱能介质的纤维向口侧投射。下行投射与起源至少三排口侧神经节中的神经元进行通信。数据表明，快速非胆碱能神经传递可能有助于蠕动反射期间六甲铵抵抗性下行抑制。
