Improving effect of huperzine A on discrimination performance in aged rats and adult rats with experimental cognitive impairment

Huperzine A (Hup-A) , a new alkaloid extracted from Huperzia serrata, is a reversible acetylcholinesterase inhibitor. By using Y-maze method, the rats were traincd to escape foot shocks by going to the light arca (safe area). The criterion of learning or memory retention was met when the rat chose the light area 10 trials in succession. The effects of Hup-A on learning and memory retention processes of brightness discrimination were studied in this paper. The results were as follows; 1) Hup-A (O.1 mg/kg ip or 0.3 mg/kg ig) given 20 min before hypercapnia prevented the CO2-induced impairment of learning of brightness discrimination tasks in rats. This improving effect was also seen with physostigmine (Phys) 0.2 mg/kg ip. 2) Hup-A 0.1-0.3 mg/kg ip immediately after training improved memory retention process in aged rats (over 18 month-old), but neither Phys 0.2 nor HupA O.05 or 0.2 mg/kg did in adult rats. 3) when the adult rats were given Hup-A 0.4 mg/kg ig and scopolamine 0.5 mg/kg ip immediately after training and tested 1 h after medicatiop, the scopolamine-induced amnesia was reversed by Hup-A. Under the same condition, the effective dose of Phys was 0.7 mg/kg ig. These results show that the improving effects of Hup-A on learning and memory retention processes are superior to those of Phys. Hup-A should be of therapeutic value in improving cognitive function in human.