Computerized analysis of the acetylcholinesterase distribution in the rabbit hippocampal region

The distribution of acetylcholinesterase (AChE) was analysed in the hippocampal region of the rabbit, employing computerized optical densitometry (COD). AChE was demonstrated histochemically according to a modification of the copper thiocholine method, and computerized analysis was performed on a selected section with the use of a graphic operating processor, resulting in images with pixel values ranging between 0 and 255, measuring 512 X 512 pixels. Examples of the densitometric analysis include presentation of pixel values in single points, in profiles through selected areas and in slicing procedures. The results of the densitometric analysis basically agreed with the subjective visual impression of different staining intensities in the sections and corresponding photomicrographs. However, the densitometric analysis provided an objective and more exact expression of the relative AChE content of the different subfields and layers of the hippocampal region. In particular, zones with the same enzyme content as well as zones differing only minimally in activity can be recognized easily and unequivocally. In view of this, the promising future uses of COD are considered briefly.