Abstract: To explain the possible molecular mechanisms of tiletamine anesthesia on the central nervous system by investigating the changes of endogenous opioid peptides content in different encephalic regions in rats. 8 Wista rats were allocated randomly from 128 Wista rats as control group. The rest rats were divided randomly into L-Enk, M-Enk, β-EP, dynA and OFQ groups，and each group of animals were divided randomly into maintenance of anesthesia group，recovery from anesthesiaⅠgroup and recovery from anesthesiaⅡgroup. The content of 5 kinds of endogenous opioid peptides in different encephalic regions in rats were measured by Enzyme-Linked Immunosorbent Assays(ELISA). The L-Enk, M-Enk, β-EP and dynA contents in the cerebral cortex and the thalamus in the anesthesia group were obviously increased as compared with control group(P<0.05 or P<0.01)，while the OFQ content was significantly decreased(P<0.05 or P<0.01).The L-Enk, M-Enk and β-EP contents in the hippocampus were obviously increased as compared with control group(P<0.05 or P<0.01)，but neither the dynA nor OFQ contents were obviously changed. The M-Enk, β-EP and dynA contents in the brainstem were obviously increased as compared with control group(P<0.05 or P<0.01)，the OFQ content was obviously decreased（P<0.05），but the L-Enk content was not changed. In both of the recovery from anesthesiaⅠgroup and anesthesiaⅡgroup the L-Enk, M-Enk, β-EP, dynA and OFQ contents in the above encephalic regions were revived as compared with control group(P>0.05).The content of 5 kinds of endogenous opioid peptides in the cerebellum were not obviously changed in the process of general anesthesia of tiletamine. The results suggest that tiletamine anesthesia have an effect on the content of 5 kinds of endogenous opioid peptides in different encephalic regions. Tiletamine could increase the L-Enk , M-Enk, β-EP and dynA contents in both of the cerebral cortex and the thalamus，and increase the L-Enk, M-Enk and β-EP contents in the hippocampus，and M-Enk, β-EP and dynA contents in the brainstem，respectively，but decrease the OFQ content in the cerebral cortex，the thalamus and the brain stem.