A dementia model was produced in adult Sprague-Dawley rats by bilateral injection of ibotenic acid

2μg in 0.5μL per side

into basal ganlion. ZDY101

3.6

18

90 mg·kg? ·d?

was given through gastric tube to 3 groups 1 1 of the model rats for 90 days. The learning and memory ability of model rats without treatment declined compared with sham-operated controls

the composite index (number of wrong reponse in 5 min divided by latent period) being 0.71±0.30 vs 0.10±0.13 respectively. The brain M receptor density also decreased as compared with sham-operated controls

being 891±150 vs 1039±214 fmol·mg? protein respectively. ZDY101 simultaneously up-regulated the 1 brain M receptor density and improved the memory and learning ability of model rats. For the middle dose group

the M receptor density was 1028±145 fmol·mg? protein (P<0.05) and the composite index of step-through test was 1 0.20±0.18 (P<0.01). Since there was a significant correlation between M-receptor density and result of step-through test

it is apparent that the mechanism of action of ZDY101 is quite different from that of cholinesterase inhibitor. It is highly probable that the improvement of memory was due to the up-regulation of brain M receptor density