Ultracytochemical demonstration of cholinesterase activity in the atrium of the guinea-pig heart

Summary The ultrastructural distribution of cholinesterase (ChE) activity was examined in the atrium of the guinea-pig heart using Karnovsky's method.The reaction products showing the ChE activity were found mainly in the neural elements in the atrium. There were axons showing no reaction products intermingled with axons showing the positive enzymatic activity. In the enzymatically positive axons, the reaction products were observed in the axon-Schwann interspace, the interspace between neighboring axons and the corresponding plasma membranes in nerve fiber bundles as well as preterminal axons. It was of interest to find that not only axons containing ordinary agranular vesicles, but also axons with larger granular vesicles showed the ChE activity.In terminals the enzymatic activity was found also in the axon-Schwann interspace, the interspace between the axolemma and the sarcolemma and the corresponding plasma membranes of the enzymatically positive areas. In the neuron the enzymatic activity was positive in the endoplasmic reticulum and the interspace between the neuronal plasma membrane and the corresponding plasma membrane of the satellite cell. Plasma membranes facing to these enzymatically positive spaces were also positive for the enzymatic activity.This investigation has been supported by a research fund from Takeda Chemical Industries, Ltd., Osaka, Japan.A part of this work has been presented at the 8th Annual Meeting of the Japan Society of Histochemistry and Cytochemistry held in Kyoto on Nov. 30–Dec. 1, 1967, and also at the 24th Annual Scientific Meeting of the Japanese Society of Electron Microscopy held in Kofu on May 11–12, 1968.