Characterization of acetylcholinesterase isoforms in septal and hippocampal cultures and cocultures.

Dissociated neurons from the hippocampus and septum of fetal mice were grown in culture, both separately and together, and the characteristics of the acetylcholinesterase (AChE) in these cells were analyzed. All 3 culture types produce extracts with 4.9S, 6.8S and 10.1S AChE isoforms. Septal cultures and septal-hippocampal cocultures contain principally (63% and 51%, respectively) the 10S isoform; whereas hippocampal cultures contain little (22%) of this AChE form. The location of the isoforms were identified by experiments using the non-permeable AChE inhibitor, echothiophate iodide, and by sequential extraction experiments. The principal form of AChE in septal cells is the 10S isoform bound on the external plasma membrane. Cells in hippocampal cultures contain little of this AChE form; the principal forms in these cells are the soluble intracellular 4-7S isoforms. Cells in septal-hippocampal cocultures have an AChE composition intermediate between the other two culture types, but resemble far more the septal than the hippocampal culture. All 3 culture types secrete the 10S isoform into the media in about the same quantities.