[Effect of naftidrofuryl oxalate (LS-121) on experimental amnesia model in rats]. 
Effects of naftidrofuryl oxalate (LS-121) on experimental amnesia models, which were induced by cycloheximide (CXM), scopolamine (SCOP) and basal-forebrain (BF) lesion, were investigated using the step-through passive avoidance response in rats.  In the retention test, a cut-off time of 600 sec was employed for the measurement of step-through latency (STL).  The animals, that showed over 300 sec of STL was regarded as having the criterion of memory retention (% of retention).  Increase in both parameters of STL and % of retention was regarded to indicate that the drug was able to improve the amnesia.  If only one of the two parameters was increased, we considered that the drug had a tendency to improve the amnesia.  Pretraining, post-training and pre-retention treatment of LS-121 (25 mg/kg) improved CXM- and SCOP-induced amnesia.  Post-training treatment of LS-121 (25 mg/kg) showed a tendency to improve the BF lesion-induced amnesia.  These results suggest that the antiamnesic action of LS-121 may be produced through an activation of the acetylcholinergic neuronal system.  Since it improved the amnesia when administered in the pre-retention test, there is a possibility that LS-121 has not only a protective effect, but also a therapeutic effect.  Furthermore, it is suggested that LS-121 may also have a therapeutic effect on Alzheimer's disease, since it showed a tendency to improve the BF lesion-induced amnesia.