Objective  To observe the change in memory of aged rats and the expression of alpha 4 acetylcholine receptor in hippocampus 5 h after inhalation of 1.2% isoflurane.   Methods  Fifty healthy adult and 50 aged SD rats were randomly divided into aged normal control group (A0)

aged water labyrinth normal control group (WA0)

1 day isoflurane aged water labyrinth group (WA1)

3-day isoflurane aged water labyrinth group (WA3)

7-day isoflurane aged water labyrinth group (WA7)

adult normal control group (B0)

  adult water labyrinth normal control group (WB0)

adult 1 day isoflurane water labyrinth group (WB1)， 3-day isoflurane water labyrinth group (WB3)

and 7-day isoflurane water labyrinth group (WB7)

10 rats in each group. Memory of rats in WA1

WA3

WA7 groups was detected 5 h after inhalation of 1.2% isoflurane while memory in rats of WB1

WB3 and WB7 groups was detected during the Morris water maze testing. The rats in A0

WA0

WA7

B0

WB0 and WB7 groups were killed on day 7 to detect the expression of α4 acetylcholine receptor by Westernblotting for observation of changes in distribution of positive immune reaction cells in hippocampus.   Results  Water maze test showed that there was no significant difference in expression of alpha 4 acetylcholine receptor between WA0 and WB0 groups. However

the expression level of alpha 4 acetylcholine receptor was significantly lower in latent period of WA1 than in latent period of WA0

WB0 and WB7 groups (P0.05). A significant change was observed in latent period of WA3 compared with WA0

WB0 and WB7 groups (P0.05). Western blot analysis showed that the expression level of alpha 4 acetylcholine receptor was not significantly different WA0

WB0

A0 and B0 groups (P0.05). However

the expression of alpha 4 acetylcholine receptor was lower in WA1（2.18±0.12）and WA3（2.21±0.11）than in WA0

WB0

A0 and B0 groups. The number of immune positive cells was not significantly different in WA0

WB0

A0 and B0 groups but was significantly lower in WA1group than in WA0

WB0

A0 and B0 groups.   Conclusion  Inhalation of 1.2% isoflurane can decrease the memory of old rats

which may be related with the decreased expression of α4 acetylcholine receptor in hippocampus.