Acetylcholinesterase stain intensity variation in the rat dentate gyrus: a quantitative description based on digital...

Three-dimensional patterns of variation in the intensity of acetylcholinesterase histochemical staining and the width of stain-defined subregions were quantified for the dentate gyrus of the adult male Long-Evans rat. Matched tissue sections sampled through the central hippocampal formation of five rats were measured with a digital image analysis computer system. The width and stain intensity were determined for defined portions of the dentate gyrus related to gross acetylcholinesterase staining patterns and the known distribution of dentate afferents. Normalized values reflecting stain intensity at defined positions within this standardized sampling array were examined to investigate regional differences in acetylcholinesterase distribution along the primary dendritic axis of dentate granule neurons. The data illustrate quantitative differences in the partitioning of acetylcholinesterase as a function of intrahippocampal position. The variation is more pronounced in the septal-temporal axis than the granule cell layer crest-tip axis. Furthermore, the septal-temporal variations in acetylcholinesterase intensity demonstrate some independence according to proximal-distal location within the molecular layer. The results suggest that acetylcholinesterase distribution within the dentate gyrus may reflect local physiological characteristics of those afferent systems related to this enzyme, including but not necessarily limited to those that are specifically cholinergic.