However, it takes at least a few hours for infarction to fully develop, and various studies have demonstrated that drugs, such as recombinant human erythropoietin [11] and huperzine A [12], a reversible and selective acetylcholinesterase (AChE) inhibitor, injected as late as 6 h after stroke, reduce infarct size [11], [12], [13]. Here, ACHE is linked to infarction.