CHOLINESTERASE IN THE HIPPOCAMPAL REGION

Abstract

The hippocampal region was examined with histochemical methods for acetylcholinesterase (AChE)in rats and 1 guinea pig. A detailed account is given of the distribution of the enzyme in terms of normal architectonics and of several of afferents, described earlier. The enzyme is not diffusely distributed in the hippocampal region but concentrated in definite layers according to a pattern changing from one cortical area to the next. Within certain areas, layers containing terminal commissural fibres are poor in AChE, whereas the enzyme is abundant in zones receiving cingulum fibres or where axonal arborizations of basket cells form axo-somatic synapses. Exceptions to these general rules in other parts of the hippocampal region are defined. The possibility that these histochemical data might constitute the basis for further experimental anatomical and electrophysiological investigations is briefly considered.