Paeoniflorin attenuates learning impairment of aged rats in operant brightness discrimination task.

The effects of paeoniflorin isolated from peony were examined on an aging-induced learning deficit in an operant brightness discrimination task in Fischer 344 rats. Learning in aged (25 months) rats was significantly impaired compared with young (5 months) rats. Daily administration of paeoniflorin (0.01 mg/kg, PO) significantly attenuated the learning impairment in aged rats, whereas it did not affect the learning in young rats. Although tacrine (0.3 and 1 mg/kg, IP), a cholinesterase inhibitor, also did not affect the learning in young rats, it slightly augmented the aging-induced learning deficit in the present task. These data indicate the therapeutic potential of paeoniflorin in the treatment of senile dementia and aging-induced cognitive dysfunction.