DISTRIBUTION OF ACETYLCHOLINESTERASE IN THE HIPPOCAMPAL REGION OF THEMOUSE .3. THE AREA DENTATA

The distribution of acetylcholinesterase (AChE) was examined in the ar ea dentata of the adult mouse (Mus musculus domesticus). A distinctly stratified distribution of the enzyme was observed and was compared in detail with cytoarchitectural fields and layers. In the stratum molec ulare, bands of relatively high AChE activity were seen immediately be neath the pia, at the borders between the outer, middle, and deep port ions of the stratum moleculare, and superficial to the granule cell la yer. AChE activity was low in the intervening parts of the stratum mol eculare. In contrast to the rat, three sublaminae could be discerned i n the hilus of the mouse at most septotemporal levels: a limiting subz one, a hilar plexiform layer, and a deep hilar cell mass. Deep to the granule cell layer, AChE activity was high in the limiting subzone and , septally, in the hilar plexiform layer. The deep hilar cell mass sta ined lightly towards the septal pole of the region but darker at more temporal levels. Numerous AChE-stained cells were seen in the hilus, w ith the exception of the most temporal levels. A comparative analysis of the AChE pattern of the area dentata reveals that 1) AChE-intense s upra- and infragranular bands are found in all mammals, whereas 2) con siderable differences between various strains of mice and between spec ies are seen in the stratum moleculare. The functional significance of the AChE pattern is discussed in relation to species differences and connectivity and also with respect to possible activities of the enzym e other than hydrolysis of ACh, which may be involved in growth-relate d functions and in the plastic and degenerative processes observed in Alzheimer's disease.