A Modification of the Thiocholine Method for the Determination of Cholinesterase. II. Histochemical Application.

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Abstract
Summary.: Based upon the biochemical controls of the thiocholine method (Holmstedt1957) the various steps of the histochemical procedure have been investigated. The inhibitors Mipafox and BW 284c51 and the substrates acetylthiocholine and butyrylthiocholine were combined as shown in Table 3 with the object of producing a reliable method of separating the two types of cholin‐esterase. Sufficient controls are included in the table to allow a distinct separation of the two types of cholinesterase.The technique of the modified thiocholine method is given in detail. The following modifications have been made.1. Inclusion of new inhibitors as above. (Mipafox and BW 284c51.)2. No presaturation with copper thiocholine.3. No development with ammonium sulphide.With the modified method, stellate ganglion, striated muscle and stomach wall have been stained in order to produce confirmation of the biochemical controls, not with the purpose of studying the morphology in detail. Comparison of sympathetic ganglia and motor end‐plates shows that the ganglion cells contain only acetylcholinesterase but that the motor end‐plates also contain a considerable amount of butyrylcholinesterase.The reasons for the alterations of the original thiocholine method are discussed. The exclusion of the presaturation with copper thiocholine produces no effect on the staining of tissue sections. The exclusion of development with ammonium sulphide diminishes diffusion artefacts to a considerable degree. Only fresh frozen sections can be used at present, if the purpose is to distinguish between the two types of cholinesterase.