Pain
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Some electrophysiologic studies demonstrate new, excitatory alpha2-adrenoceptors on peripheral nociceptors and their dorsal root ganglion (DRG) cell bodies after nerve injury, yet administration of alpha2-adrenoceptor agonists at these sites reduces hypersensitivity rather than worsens it. Since TRPV-1 expressing nociceptor afferents are important in many pain states, we examined the expression of this channel and its co-expression with alpha2C-adrenoceptors in injured DRG cell bodies and the ability of alpha2-adrenoceptors to inhibit responses to stimulation. Rats underwent tight ligation of the left L5 and L6 spinal nerves, followed by behavioral testing, removal of L5 and L6 DRGs, and either immunostaining for TRPV-1 channels and alpha2C-adrenoceptors or intracellular calcium videomicroscopy in response to electrical field stimulation before and after perfusion with clonidine and capsaicin. ⋯ The proportion of clonidine inhibited cells which responded to capsaicin increased 5 fold after injury. We conclude that TRPV-1 and alpha2C-adrenoceptors are up-regulated in some injured medium and large size neurons after nerve ligation. Increased co-expression by immunocytochemistry, and increased proportion of cells inhibited by clonidine and expressing functional TRPV-1 channels suggest that these cells may play an important role in the analgesic effects of alpha2-adrenoceptor agonists in neuropathic pain.
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Comparative Study
Intrathecal morphine and ketorolac analgesia after surgery: comparison of spontaneous and elicited responses in rats.
Pain after surgery results in significant morbidity, and systemic opioids often fail to provide adequate analgesia without marked sedation and respiratory depression. Intrathecal morphine provides better analgesia, but is limited by delayed respiratory depression. Intrathecal injection of the cyclooxygenase inhibitor, ketorolac, has recently entered clinical trials, and the current study examined the interaction between intrathecal morphine and ketorolac to treat postoperative pain. ⋯ These data confirm that spinal opioid receptor and cyclooxygenase enzyme inhibition diminish elicited tactile hypersensitivity after surgery, and that they similarly return spontaneous behavior to normal. Differences in drug potency could reflect fundamental differences in outcome measures or in the surgical procedures themselves. These data support combination study of intrathecal morphine and ketorolac for postoperative pain.
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Randomized Controlled Trial Comparative Study Clinical Trial
Rofecoxib attenuates both primary and secondary inflammatory hyperalgesia: a randomized, double blinded, placebo controlled crossover trial in the UV-B pain model.
The analysis of drug's influence on peripheral and central sensitisation can give useful information about its mode of action and can lead to more efficacy in the treatment of pain. Peripheral inflammation is associated with peripheral expression and up-regulation of cyclooxygenase 2 (COX-2) in the CNS. The relative contribution of COX-2 mediated central sensitisation may be prominent under inflammatory conditions. ⋯ No significant difference between the three dosage groups was observed. These data confirm peripheral effects of rofecoxib in a human inflammatory UV-B pain model and provide circumstantial evidence that even a standard clinical dose of rofecoxib reduces central hyperalgesia in inflammatory pain. We confirm that the effect of single oral dose of rofecoxib plateaus at 50 mg.
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Randomized Controlled Trial Comparative Study Clinical Trial
A trial of an activating intervention for chronic back pain in primary care and physical therapy settings.
In primary care and physical therapy settings, we evaluated an intervention for chronic back pain patients which incorporated fear reducing and activating techniques. Primary care patients seen for back pain in primary care were screened to identify persons with significant activity limitations 8-10 weeks after their visit. Eligible and willing patients were randomized (N=240). ⋯ The adjusted mean difference in activity limitation days was 4.5 days at 6 months, 2.8 days at 12 months, and 6.9 days at 24 months. No differences were observed in the percent unemployed or the percent receiving worker's compensation or disability benefits, but these outcomes were relatively uncommon. We conclude that an intervention integrating fear reducing and activating interventions into care for chronic back pain patients produced sustained reductions in patient fears, common activity limitations related to back pain, and days missed from usual activities due to back pain.
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Comparative Study
Confirmatory factor analysis of the Pain Catastrophizing Scale in African American and Caucasian Workers' Compensation claimants with low back injuries.
Pain catastrophizing is an important cognitive construct that has been linked with many aspects of the pain experience, including pain intensity, emotional distress, pain-related disability, and pain behavior. The Pain Catastrophizing Scale (PCS), an instrument often used to assess this construct, reflects three aspects of catastrophizing: Rumination, Magnification, and Helplessness. ⋯ Results indicated that a two-factor model of the PCS (Rumination and 'Powerlessness,' the latter a combination of the PCS Magnification and Helplessness scores) was the most parsimonious fit to the data, particularly in the African American sample. Future research in other clinical samples that include African Americans is needed to examine the stability of the results reported here.