A leptin-mediated central mechanism in analgesia-enhanced opioid reward in rats.

Opioid analgesics are commonly used in chronic pain management despite a potential risk of rewarding. However, it remains unclear whether opioid analgesia would enhance the opioid rewarding effect thereby contributing to opioid rewarding. Utilizing a rat paradigm of conditioned place preference (CPP) combined with ankle monoarthritis as a condition of persistent nociception, we showed that analgesia induced by either morphine or the nonsteroid anti-inflammatory drug ibuprofen increased CPP scores in arthritic rats, suggesting that analgesia itself had a rewarding effect. However, arthritic rats exhibited a significantly higher CPP score in response to morphine than ibuprofen. Thus, the rewarding effect of morphine was enhanced in the presence of persistent nociception, producing a phenomenon of analgesia-enhanced opioid reward. At the cellular level, administration of morphine activated a cascade of leptin expression, glial activation, and dopamine receptor upregulation in the nucleus accumbens (NAc), while administration of ibuprofen decreased glial activation with no effect on leptin expression in the NAc. Furthermore, the morphine rewarding effect was blocked in leptin deficient ob/ob mice or by neutralizing leptin or interleukin-1ß in the NAc without diminishing morphine analgesia. The data indicate that systemic opioid can activate a leptin-mediated central mechanism in the NAc that led to the enhanced opioid rewarding effect. These findings provide evidence for an interaction between opioid analgesia and opioid rewarding, which may have implications in clinical opioid dose escalation in chronic pain management.

Perioperative red blood cell transfusion for patients undergoing elective non-cardiac surgery: an audit at a Chinese tertiary hospital.

Perioperative blood transfusion still takes a large proportion in inappropriate blood transfusion. As the data are limited in China, we reported a perioperative red blood cell (RBC) transfusion practices in a tertiary hospital in Guangzhou, China. In 2008-2009, patients who underwent elective surgeries receiving RBC transfusions were recorded and the rate of overtransfusion was analyzed. Overtransfusion was defined as discharge hemoglobin (Hb) exceeding 10 g/dL. The median amount of RBC transfused perioperatively was four units in all 2572 patients. The overall rate of overtransfusion was 48.6% and the Department of Neurosurgery had the highest overtransfusion rate. These results are of great use for the future management of blood resource.

Intravenous flurbiprofen for post-thymectomy pain relief in patients with myasthenia gravis.

BACKGROUND: Post-thymectomy pain in myasthenia gravis (MG) patients can inhibit breathing and coughing. Inappropriate usage of analgesics may exacerbate respiratory inhibition and even cause myasthenic crisis. Flurbiprofen is a non-steroidal anti-inflammatory drug (NSAID) that is commonly used to control moderate postoperative pain and is not associated with respiratory inhibition. We hypothesized that flurbiprofen may provide post-thymectomy pain relief without increasing the risk of complications in MG patients. METHODS: Two hundred MG patients underwent extended thymectomy from March 2006 to December 2010 and were randomly allocated to a flurbiprofen group (110 patients, 50 mg intravenous flurbiprofen axetil) or a control group (90 patients, 100 mg intramuscular tramadol) as postoperative analgesia. Visual analog scale (VAS) pain score, heart rate, blood pressure, respiratory rate, pulse oximetry (SpO2), and adverse effects were recorded before and up to 24 h after drug administration. RESULTS: There were no significant differences in the preoperative clinical characteristics of the flurbiprofen and control (tramadol) groups. Both flurbiprofen and tramadol significantly alleviated post-thymectomy pain (p<0.05 for both), but patients in flurbiprofen group had significantly lower VAS pain scores at 0.5 h, 2 h, 4 h, and 8 h after surgery (p<0.05 for all times). There were no significant post-thymectomy changes of heart rate, respiratory rate, mean arterial blood pressure, or SpO2 in either group at all time points. CONCLUSIONS: Post-thymectomy intravenous administration of flurbiprofen axetil provides safe and effective analgesia for MG patients.

Spatiotemporal pattern of concurrent spinal and supraspinal NF-κB expression after peripheral nerve injury.

UNLABELLED: The expression of NF-κB in the spinal cord is associated with neuropathic pain. However, little is known about its expression beyond the spinal cord. Here we examined a spatial and temporal pattern of the NF-κB expression in both spinal and supraspinal regions. After chronic constriction injury (CCI) of the sciatic nerve, NF-κB (p65) expression was significantly increased in the ipsilateral spinal cord. In contrast, the NF-κB expression in the contralateral primary somatosensory cortex was decreased with no significant differences seen in the thalamus. In the contralateral anterior cingulate cortex, the NF-κB expression was increased significantly on day 14 as compared with the sham group. In the contralateral amygdala, the NF-κB expression showed a time-dependent downregulation after CCI, which became significant on day 14. MK-801 reduced nociceptive behaviors and reversed the direction of NF-κB expression. These results indicate that the CCI-induced expression of p65 NF-κB is both time-dependent and region-specific, in areas that process both sensory-discriminative and motivational-affective dimensions of pain. PERSPECTIVE: This article presents a spatiotemporal mapping of the NF-κB expression in spinal and supraspinal regions after peripheral nerve injury. These findings point to an involvement of NF-κB beyond the spinal cord in both the sensory discriminative and emotional affective aspects of neuropathic pain processing.

Peripheral nerve injury alters the expression of NF-κB in the rat's hippocampus.

The hippocampus plays an important role in learning and memory and possibly contributes to the formation of pain-related memory and emotional responses. However, there is currently little data linking the hippocampus to neuropathic pain. It has been reported that NF-κB is an important regulatory factor in memory consolidation within the hippocampus. This study aims to examine a possible relationship between the hippocampal NF-κB expression and nerve injury-induced thermal hyperalgesia using a rat model of constriction sciatic nerve injury (CCI). Immunofluorescence and Western blot analysis were performed to detect and quantify the hippocampal NF-κB expression. Thermal hyperalgesia was examined on day 0 and postoperative days 1, 7 and 14. The nuclear portion of the p65 NF-κB expression was significantly increased on the contralateral side on days 7 and 14 as well as significantly increased on the ipsilateral side on day 14 as compared to the sham control group. Intraperitoneal administration of MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist, reduced hyperalgesia and modulated the NF-κB expression in the contralateral side of hippocampus. These results suggest an association between the hippocampal NF-κB expression and the behavioral manifestation of thermal hyperalgesia, which is likely to be mediated through activation of the NMDA receptor.

A combined effect of dextromethorphan and melatonin on neuropathic pain behavior in rats.

Previous study has shown that administration of melatonin into the anterior cingulate cortex contralateral to peripheral nerve injury prevented exacerbation of mechanical allodynia with a concurrent improvement of depression-like behavior in Wistar-Kyoto (WKY) rats, a genetic variation of Wistar rats. In the present study, we examined the effect of the individual versus combined treatment of melatonin and/or dextromethorphan (DM), a clinically available N-methyl-d-aspartate (NMDA) receptor antagonist, on pain behaviors in WKY rats with chronic constriction sciatic nerve injury (CCI). Pain behaviors (thermal hyperalgesia and mechanical allodynia) were established at one week after CCI. WKY rats were then treated intraperitoneally with various doses of melatonin, DM or their combination once daily for the following week. At the end of this one-week treatment, behavioral tests were repeated in these same rats. While DM alone was effective in reducing thermal hyperalgesia at three tested doses (15, 30 or 60 mg/kg), it reduced mechanical allodynia only at high doses (30 or 60 mg/kg). By comparison, administration of melatonin alone was effective in reducing thermal hyperalgesia only at the highest dose (120 mg/kg, but not 30 or 60 mg/kg) tested in this experiment. Melatonin alone failed to reverse allodynia at all three tested doses (30, 60 and 120 mg/kg). However, the combined intraperitoneal administration of melatonin (30 mg/kg) and DM (15 mg/kg) effectively reversed both thermal hyperalgesia and mechanical allodynia although each individual dose alone did not reduce pain behaviors. These results suggest that a combination of melatonin with a clinically available NMDA receptor antagonist might be more effective than either drug alone for the treatment of neuropathic pain.