Abstract: The change of 2-¹⁸F-A-85380 in chronic ischemia rats with cognitive dysfunction was evaluated by Micro-PET. Chronic cerebral ischemia rat model was made by bilateral common carotid artery ligation. Four weeks later, Morris water experiments were performed to check cognitive dysfunction. After intravenous injection of 37 MBq 2-¹⁸F-A-85380, the normal isoflurane-anesthetized rat underwent Micro-PET scan. The brain scanning was performed for 10 minutes at 30, 60, 120, 180, 240 minutes after injection. Select the thalamus, frontal cortex, cerebellum as region of interesting for quantitative analysis. The chronic ischemia rats underwent Micro-PET scan for 10 minutes at 120 minutes. SUV_{ave thalamus}/SUV_{ave cerebellum}, SUV_{ave frontal cortex}/SUV_{ave cerebellum} were calculated. Four weeks after the surgical procedure, Morris water maze was used to assess working memory tasks with two groups of rats. The escape latency of the chronic ischemia group and the normal group at the fifth day was (24.16±27.18) s, (9.44±5.48) s, respectively. The chronic ischemia group compared with the normal group, the difference was statistically significant. The ischemic group in learning to find the platform slower than the normal rats. At the sixth day, the chronic ischemia rats by looking for the original platform quadrant after removed the platform, was slower than the normal group in Morris space exploration experiments. The chronic ischemia group was (2.60±1.67) times, the normal group was (6.20±2.95) times, the difference was statistically significant. By the Micro-PET scanning, the thalamus could be distinguished markedly during 120 minutes to 240 minutes, especially at 120 minutes. At 120 minutes, SUV_{ave thalamus}/SUV_{ave cerebellum}, SUV_{ave frontal cortex}/SUV_{ave cerebellum} of the chronic ischemia cognitive dysfunction rats was 1.27±0.02, 1.07±0.03, respectively. The SUV_{ave thalamus}/SUV_{ave cerebellum}, SUV_{ave frontal cortex}/SUV_{ave cerebellum} of the nomal group was 1.62±0.06 and 1.34±0.28, respectively. The difference was statistically significant. 2-¹⁸F-A-85380 is suitable for nAChRs imaging. The suitable time for rats Micro-PET imaging in vivo was 120~240 minutes, especially at 120 minutes.The quantitative analysis of nAChRs in different brain regions of rats was performed in vivo, which is very useful for detecting the changes of variety receptors in chronic ischemia cognitive dysfunction rats, meanwhile lay the foundation for investigating chronic ischemia cognitive dysfunction rats in various stages or evaluating the efficacy of treatment in chronic ischemia cognitive dysfunction rats.