RESUMO
<p><b>OBJECTIVE</b>To explore the central mechanism of postoperative fatigue syndrome by detecting the expression of NMDA receptor and tryptophan metabolism.</p><p><b>METHODS</b>After being numbered according to the weight, ninety-six male SD rats were randomly divided into control group (bowel loop was flipped after laparotomy and received intraperitoneal injection of saline at a dose of 1 ml/kg), POFS model(70% of the length of small intestine was resected and received intraperitoneal injection of saline at a dose of 1 ml/kg), and NMDA antagonist groups(70% of the length of small intestine was resected and received intraperitoneal injection of MK801 at a dose of 1 ml/kg). Each group was divided into subgroups by postoperative 1, 3, 5 and 7 d, with 8 rats in each subgroup. The hippocampus was removed at each time point after open field test (OFT) to detect the mRNA expression levels of NMDA receptor 1 and kynurenine aminotransferase III((KATIII() by real-time PCR. Protein level of NMDA receptor 1 was detected by Western blot. High performance liquid chromatography (HPLC) was used to measure the concentrations of tryptophan (TRP), kynurenine (KYN) and kynurenic acid(KYNA). Ultra-structural changes of hippocampal neurons were observed by transmission electron microscopy(TEM).</p><p><b>RESULTS</b>As compared to control group, exercise score decreased(P<0.05), rest time and central panel residence time prolonged, periphery/central panel ratio increased (all P<0.05), mRNA and protein expressions of NMDA receptor 1 increased (P<0.05), mRNA expression of KAT III( decreased (P<0.05), KYN/TRP ratio and KYN/KYNA ratio decreased (all P<0.05) in POFS group on postoperative day 1 and 3. As compared to POFS group, central panel residence time and periphery/central panel ratio decreased on postoperative day 1, and mRNA and protein expressions of NMDA receptor 1 decreased on postoperative day 1 and 3 (all P<0.05) in antagonist group. TEM revealed that degenerated neuron was found in the hippocampus of POFS rats, while such damage was improved in antagonist group.</p><p><b>CONCLUSION</b>The increased expression level of NMDA receptor may play an important role in POFS. NMDA receptor antagonist MK801 may improve the POFS.</p>