Abstract: OBJECTIVE: To study the effects of cigarette smoke exposure and chronic stress on learning and memory in rats. METHODS: 40 SPF SD rats,10 in each group,50% males,were randomly divided into non-exposed control,cigarette smoke,chronic stress and the combined groups. Rats in the cigarette smoke group were exposed to the virus by respiratory statics,once a day,10 cigarettes each time for 1 h,for 12 weeks. In the chronic stress group,one chronic stress was randomly given every day from five chronic stress programs,and each chronic stress mode was applied discontinuously for 12 weeks. The combined group was treated with chronic stress and smoked 10 cigarettes a day,for 12 weeks. In the 2,4,8,10,12 weeks,the Morris water maze experiment in rats was conducted,constituting the escape latency of rats,test of 4 group rats' learning and memory ability,infected after 12 weeks,abdominal aortic blood,wring the brain,rat body mass,brain,brain viscera coefficient,brain tissue pathology changes,and determination of Cort concentrations,ACH,CHAT content and ACHE activity in serum. RESULTS: Compared with the control group,Cort concentrations in the chronic stress group was significantly increased (P < 0.05),indicating that the rats in the chronic stress group were under stress. Compared with the chronic stress group,the latency of escape at week 2 in the combined group was decreased and showed an antagonistic effect (P < 0.05). Compared with the control group,the latencies of escape at week 10 in the three treated groups were increased (P < 0.05). Pathology results from the cigarette smoke group show rat neurons mild nuclear pyknosis,meningeal vascular moderate hyperemia and mild bleeding,glial cell hyperplasia,chronic stress group rats neurons,visible light nuclear pyknosis and congested,joint intervention group change is most obvious,joint intervention group rat neurons moderate nucleus pyknosis,meningeal congestion and edema of the mild,neurons around the cavity formation. Compared with the control group,the ACH content of rats in the three treated groups were decreased (P < 0.05),while the CHAT content of rats in the stress group decreased and ACHE activity increased (P < 0.05). CONCLUSION: The effects of combined cigarette smoke and chronic stress were interactive on the learning and memory ability of rats. In addition,learning and memory in rats were reduced in the three treated groups. Furthermore,the synthesis of ACH was impaired which was associated with reduced learning and memory ability of rats. The combined exposure did not interact with ACH,CHAT content and ACHE activity. The specific mechanism of its joint action needs to be further studied.

Key words: cigarette smoke, chronic stress, joint role, learning and memory ability