The ameliorating effects of LiuWei Dihuang Wang (LDW) after single, one-week or two-week treatment of scopolamine (SCOP)-induced and p-chloroamphetamine (PCA)-induced amnesia by using the passive avoidance task and the facilitatory effects on two-way active avoidance performance in rats were studied. LDW (2 g/kg) after single treatment significantly prolonged the shortened step-through latency induced by SCOP and PCA. Then, SCOP- and PCA-induced amnesia was reversed by 1 and 0.1—1 g/kg LDW with one-week consecutive treatment respectively. For two-week consecutive treatment with LDW, the reversal from SCOP- and PCA-induced amnesia required only 0.01 g/kg. However, the rats treated with LDW only at 0.5, but not 0.01—0.1 g/kg, before or after each training session showed an increasing number of avoidances and a decreasing number of escapes on days 2—5 of learning. LDW at any dose alone did not influence the step-through latency in the training trial produced by non-shock rats, the motor activity and pentobarbital-induced hypnosis in rodents. These results suggest that LDW possesses the anti-amnestic and cognitive-enhancing activities related to the memory processes, and these activities were parallel to treatment duration and dependent on the learning models.
