Objective: To investigate the changes of serum substance P (Substance P, SP) content and its effects on sedation and hypnosis after mice inhale Isoflurane. Methods: 45 mice were randomly divided into Isoflurane (Isoflurane, Iso) group, Dexmedetomidine (Dexmedetomidine, Dex) group and Isoflurane combined with substance P receptor antagonist agent (Antagonist of Substance P, Iso+A-SP) group; using ELISA method to detect serum substance P content of groups of mice, applying analepsia experiment to

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... record sleep time of groups of mice, applying Hot-plate and writhing test to record threshold of pain in Hot-plate method and writhing frequency of groups of mice. Brain stereotaxic, nucleus spile, micro-injection and polysomnography were used to apply in the blank control group (PBS), substance P group (SP group), substance P receptor antagonist agent group (A-SP group), 3-Mercaptopropionic acid group (3-MP group) and substance P+3-Mercaptopropionic acid group (SP+3-MP group) for observing the mechanism of action of SP on sleep of mice. Results: Iso group had the strongest sedation and the Iso+A-SP group was the weakest. For writhing frequency, Dex group and Iso+A-SP group were significantly more than that of the Iso group, while Iso+A-SP group was more than that of the Dex group; after medication, the threshold of pain in Iso+A-SP group had no significant difference compared with medication before, while Iso group and Dex group were prolonged pain threshold; Iso group and Dex group pain threshold were the longest when the medication for 10 minutes, the above difference was statistically significant (P<0.05); the sleep time of Iso group was longer than that of Iso+A-SP group and Dex group, the sleep time of Iso+A-SP group was the shortest, and there was statistical difference (P<0.05); before medication, there was no significant difference in the concentration of substance P in each group; after medication, Iso group and Iso+A-SP group of P substance concentration difference was quite little, but Iso group and Iso+A-SP group were significantly higher than the Dex group, the difference was statistically significant (P<0.05). Compared with the control group (PBS group), sleep time of micro-injection SP (SP group) in the ventrolateral preoptic area (vLPO) in mice was significantly increased while the awakening time was significantly decreased; compared with the control group (PBS group), sleep time of micro-injection ASP (A-SP group) in vLPO was significantly decreased while the awakening time was significantly increased; compared with the 3-MP group, in the vLPO micro-injection of gamma aminobutyric acid (GABA) compounded key enzyme inhibitors substance P+3-Mercaptopropionic acid group (SP+3-MP group), the sleep time was significantly decreased while the awakening time was significantly increased, the differences mentioned above were statistical significance (P<0.05). Conclusions: Sedative and hypnotic effects of Isoflurane had close relationship with the level of substance P in the body, these effects might be achieved by the substance P, which mediated GABA neurons in vLPO.