Effects of tenuifolin extracted from radix polygalae on learning and memory: a behavioral and biochemical study on aged and amnesic mice.

Although normal cognitive changes take place when a person becomes older, aging in humans is generally associated with deterioration of cognitive performance and, in particular, of learning and memory. These cognitive deficits can cause debilitating consequences due to aging. There are a number of herbal medicines which are reported to improve brain function including intelligence. In the present study, improving effects of tenuifolin, extracted from Radix Polygalae (RP), on learning and memory in aged and dysmnesia mice were determined using step-down type passive avoidance test or Y type maze trial. Oral administration of tenuifolin (0.02, 0.04, 0.08 g/kgd(-1), for 15 d) evidently improved the latency and number of errors in aged and dysmnesia mice. The levels of cortical acetylcholine esterase (AChE) activity and hippocampal neurotransmitters in aged mice given tenuifolin (0.02, 0.04, 0.08 g/kgd(-1), for 15 d) were also investigated, and increased levels of norepinephrine (NE), dopamine (DA), decreased activity of AChE were found. However, serotonin (5-HT) had no significant difference from that of aged mice given distilled water. The evident improvement of learning and memory of aged mice is carried out by the effects of tenuifolin on the three stages of memory process, that is, acquisition, consolidation and retrieval. This may do so by relatively increasing the levels of NE, DA in the hippocampus and by decreasing the activity of AChE in the cortex.