ACHE and Alzheimer disease: In this study we investigated the structure-activity relationships by using the Electron- Topological Method [7-17] for a class of AChE inhibitors related to tacrine (9-amino-1, 2, 3, 4-tetrahydroacridine) analogues [6] and 11 H-Indeno-[1,2-b]-quinolin-10-ylamine analogues that tetracyclic tacrine analogues [18, 19], a drug currently in use for the treatment of the AD.