The journal of pain : official journal of the American Pain Society
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The chemotherapeutic agent, oxaliplatin, produces a robust painful neuropathy that results in the loss of intraepidermal nerve fibers (IENFs). We have previously reported that an acupuncture point (acupoint) injection of diluted bee venom (DBV) produces a temporary antiallodynic effect in oxaliplatin-induced neuropathic mice. Herein we show a significant long-lasting antinociceptive effect of repetitive DBV acupoint treatment on oxaliplatin-induced mechanical allodynia and a significant reduction in the loss of IENFs. DBV (0.1 mg/kg, subcutaneous) was administered once a day for 18 days beginning on day 15 after oxaliplatin injection. Immunohistochemistry for IENF was performed on the glabrous skin of the hind paw footpad using the pan-neuronal marker, protein gene product 9.5. A temporary increase in mechanical threshold was observed 60 minutes after a single DBV injection into the Zusanli acupoint, and this effect was enhanced over time with repetitive DBV treatments. The basal mechanical threshold before daily DBV injection also increased from day 7 after DBV injections, and peaked at day 14 after DBV treatment. Moreover, the oxaliplatin-induced loss of IENFs was significantly reduced in mice treated repetitively with DBV. Repetitive pretreatment with the α-2 adrenoceptor antagonist, yohimbine, (5 mg/kg, subcutaneous) completely prevented the antiallodynic effects and the increase in IENFs observed in mice treated repetitively with DBV. ⋯ We showed that repetitive acupoint stimulation with DBV gradually and significantly reduced oxaliplatin-induced mechanical allodynia and restored the loss of IENFs in neuropathic mice via an α-2 adrenoceptor mechanism. Collectively, results of this study suggest that repetitive acupoint treatment with DBV can be a potential strategy for the management of chemotherapy-induced neuropathy.
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Recent data show that dry eye (DE) susceptibility and other chronic pain syndromes (CPS) such as chronic widespread pain, irritable bowel syndrome, and pelvic pain, might share common heritable factors. Previously, we showed that DE patients described more severe symptoms and tended to report features of neuropathic ocular pain (NOP). We hypothesized that patients with a greater number of CPS would have a different DE phenotype compared with those with fewer CPS. We recruited a cohort of 154 DE patients from the Miami Veterans Affairs Hospital and defined high and low CPS groups using cluster analysis. In addition to worse nonocular pain complaints and higher post-traumatic stress disorder and depression scores (P < .01), we found that the high CPS group reported more severe neuropathic type DE symptoms compared with the low CPS group, including worse ocular pain assessed via 3 different pain scales (P < .05), with similar objective corneal DE signs. To our knowledge, this was the first study to show that DE patients who manifest a greater number of comorbid CPS reported more severe DE symptoms and features of NOP. These findings provided further evidence that NOP might represent a central pain disorder, and that shared mechanistic factors might underlie vulnerability to some forms of DE and other comorbid CPS. ⋯ DE patients reported more frequent CPS (high CPS group) and reported worse DE symptoms and ocular and nonocular pain scores. The high CPS group reported symptoms of NOP that share causal genetic factors with comorbid CPS. These results imply that an NOP evaluation and treatment should be considered for DE patients.
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Thiazolidinedione drugs (TZDs) such as pioglitazone are approved by the U.S. Food and Drug Administration for the treatment of insulin resistance in type 2 diabetes. However, whether TZDs reduce painful diabetic neuropathy (PDN) remains unknown. Therefore, we tested the hypothesis that chronic administration of pioglitazone would reduce PDN in Zucker Diabetic Fatty (ZDF(fa/fa) [ZDF]) rats. Compared with Zucker Lean (ZL(fa/+)) controls, ZDF rats developed: (1) increased blood glucose, hemoglobin A1c, methylglyoxal, and insulin levels; (2) mechanical and thermal hyperalgesia in the hind paw; (3) increased avoidance of noxious mechanical probes in a mechanical conflict avoidance behavioral assay, to our knowledge, the first report of a measure of affective-motivational pain-like behavior in ZDF rats; and (4) exaggerated lumbar dorsal horn immunohistochemical expression of pressure-evoked phosphorylated extracellular signal-regulated kinase. Seven weeks of pioglitazone (30 mg/kg/d in food) reduced blood glucose, hemoglobin A1c, hyperalgesia, and phosphorylated extracellular signal-regulated kinase expression in ZDF. To our knowledge, this is the first report to reveal hyperalgesia and spinal sensitization in the same ZDF animals, both evoked by a noxious mechanical stimulus that reflects pressure pain frequently associated with clinical PDN. Because pioglitazone provides the combined benefit of reducing hyperglycemia, hyperalgesia, and central sensitization, we suggest that TZDs represent an attractive pharmacotherapy in patients with type 2 diabetes-associated pain. ⋯ To our knowledge, this is the first preclinical report to show that: (1) ZDF rats exhibit hyperalgesia and affective-motivational pain concurrent with central sensitization; and (2) pioglitazone reduces hyperalgesia and spinal sensitization to noxious mechanical stimulation within the same subjects. Further studies are needed to determine the anti-PDN effect of TZDs in humans.
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Ginsenoside-Rb1 (Rb1) has anti-inflammatory effects. However, the potential antinociceptive value of Rb1 for the treatment of acute inflammatory nociception is still unknown. In this study, we examined whether Rb1 has any antinociceptive effects on acute inflammatory nociception in Sprague Dawley rats given intrathecal (i.t.) introduction of Rb1 (2, 10, and 50 μg) 20 minutes before injection of formalin (5%, 50 μL) into the plantar surface of the hind paws. I.t. introduction of Rb1 significantly decreased nociceptive behavior during phase II (16-60 minutes), but not phase I (0-10 minutes), after formalin stimulation, corresponding to the reduced activation of c-Fos in the L4 to L5 spinal dorsal horn after formalin stimulation. Rb1 also reduced the phosphorylation of extracellular signal-regulated kinase in the neurons, but not the microglia and astrocytes. Microscopic examination of the microglia and astrocytes revealed no morphological changes due to formalin stimulation and i.t. introduction of Rb1. Interestingly, Rb1 activated the nuclear factor erythroid 2-related factor 2 pathway and inhibited nuclear factor kappa B pathways. ⋯ Our findings indicate that i.t. introduction of Rb1 might effectively inhibit formalin-induced acute inflammatory nociception by inhibition of neuronal extracellular signal-regulated kinase phosphorylation, which is thought to regulate the nuclear factor erythroid 2-related factor 2 nuclear factor kappa B pathways in the spinal dorsal horn, which suggests therapeutic potential for suppression of acute inflammatory pain.
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Observational Study
The influence of chronic pain on post-operative pain and function after hip surgery: a prospective observational cohort study.
Pre-existing or chronic pain is an established risk factor for severe postoperative pain. In this prospective observational cohort study, we investigated whether a history of chronic pain, beyond the presence of hip-related pain, affected other postoperative factors including early mobilization, function, and psychological distress after hip surgery. Patients who underwent total hip replacement surgery were observed from the preoperative day until the seventh postoperative day. Before surgery, they were characterized by their pain history, pain intensity, function, and psychological characteristics. Postoperatively, pain intensity was evaluated on day 1, 3, 5, and 7 and the analgesic consumption was recorded for each of these days. Measures of function (functional questionnaire, ability to mobilize and to climb stairs, and range of hip motion) and psychological distress were re-evaluated on day 7. A history of chronic pain was associated with slower postoperative mobilization, poorer physical function, and greater psychological distress in addition to increased postoperative pain intensity. The comorbidity of a chronic pain disorder resulted in greater pain intensity after surgery, and also impeded postoperative rehabilitation. Identification of patients with a chronic pain disorder is necessary preoperatively so that appropriate pain management and rehabilitation can be planned to facilitate recovery. ⋯ Chronic pain, beyond the presence of hip-related pain, is associated with slower postoperative mobilization, poorer physical function, and greater psychological distress after total hip replacement surgery. Identification of patients with chronic pain and establishment of multiprofessional perioperative management might improve postoperative rehabilitation of patients with chronic pain.