Summary

Abstract

A review of the acetylthiocholinesterase (AThChE) distribution in the brain stem of the cat was carried out on material stained with Koelle and Friedenwald’s technique (1949) and with the cresylecht violet and luxol fast blue methods. The regional differences were outstanding and, in general, difficult to correlate with any existing hodological classifications. The only generalization that appears plausible applies to the motoneuronal centers which always showed a marked stain. The nuclei implicated in the auditory pathway were, with a few exceptions, poorer in enzyme than most other regions of the brain stem. The reticular formation (isodendritic core) retained its diffuse characteristics. In its caudal portion, no particular subdivisions could be proposed on the basis of the enzyme distribution. But, the rostral portion (tegmentum) could be subdivided into a number of sub-regions, according to their enzyme content. Nevertheless, no sharp borderlines could be established. For this reason, the term “tegmentum” has been retained in this report. A new nomenclature, which takes into account both histochemical and topographical factors, has been proposed to describe the various regions of this rostral portion of the reticular formation.