Abstract: AIMTo observe the effect of tenuigenin (TEN), an active component isolated from Yuanzhi, on cholinergic function in rats with β-amyloid peptide and ibotenic acid injection into right nucleus basalis magnocellularis (NBM). METHODSA combined injection of β-AP_1～40 and ibotenic acid into the right NBM was used as a dementia-like rat model. The ability of learning and memory was detected by the step-through test. The activity of choline acetyltransferase (ChAT) and the muscarinic receptor density were determined by ³H-acetylcoenzyme and ［³H］-quinuclidinyl benzilate (³H-QNB) binding tests, respectively. The activity of acetylcholinesterase (AChE) was determined by improved Ellman's method. RESULTSThe model animals were treated with daily oral administration of TEN for 60 d. The learning and memory ability were obviously improved. i.e., in the step-through test, the number of error was obviously decreased and the latency was obviously prolonged. The muscarinic receptor density and the activity of ChAT within rats brain were markedly enhanced, whereas the activity of AChE in rat brain was significantly inhibited. CONCLUSIONThese results suggest that TEN probably have certain improving and treating action for the reductions in cholinergic function in Alzheimer's disease.