Protective effect of Oren-gedoku-to (Huang-Lian-Jie-Du-Tang) against impairment of learning and memory induced by transient cerebral ischemia in mice.

The protective effect of Oren-gedoku-to (OGT; Huang-Lian-Jie-Du-Tang), a traditional Chinese medicine, against impairment of learning and memory induced by transient cerebral ischemia was investigated in mice. The cerebral ischemia caused a reduction of step-down latency and an increase of step-down errors in the passive avoidance task. Pretreatment with oral administration of OGT (2, 4 or 8 g of herbs per kg) once daily for 5 days prolonged the step-down latency significantly and decreased the step-down errors as compared with those of sham-operated controls. In the Morris water maze test, the cerebral ischemia caused an increase in the latency until finding the platform in the training trial and a decrease in the percentage of swimming in the quadrant of the former platform in the probe trial. Oren-gedoku-to (OGT; 2, 4 and 8 g/kg, p. o.) shortened the latency of escaping markedly onto the platform in the training trial and increased the percentage of crossing the former platform quadrant in the probe trial. A reference drug, tacrine (0.5 and 1.0 mg/kg, p.o.), prevented the reduction of step-down latency in the passive avoidance task and shortened the escape latency in the Morris water maze task. Furthermore, OGT significantly protected against cerebral ischemia-induced reduction in the acetylcholine (ACh) content of the cerebral cortex, hippocampus and striatum. These results indicate that the protective effects of OGT against the impairment of learning and memory induced by transient cerebral ischemia may be associated with preventing the decrease in the ACh content of the mouse brain.