Effect of Choto‐san, a Kampo medicine, on impairment of passive avoidance performance in senescence accelerated mouse (SAM)

Effect of Choto-san (TJ-47), a Kampo medicine, on impairment of learning performance was evaluated by means of a step-through passive avoidance task in SAMP8 mice, a senescence-prone substrain. Tokishakuyaku-san (TJ-23), another Kampo medicine, was also employed for comparison. SAMP8 mice at the age of 10-12 months showed a poorer passive avoidance response than SAMR1 mice, a senescence-resistant substrain, in the memory-retention test, but not in the memory-acquisition test. Improved response in the memory-retention test was observed in SAMP8 mice treated with TJ-47, and almost equal degree of improvement was also observed after treatment with TJ-23. These results suggest that a long-term administration of Choto-san could improve to some extent the impairment of memory caused by aging.