The journal of pain : official journal of the American Pain Society
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Characterization of a model of chronic orofacial hyperalgesia in the rat: contribution of NA(V) 1.8.
The purpose of this study was to develop and characterize a model of orofacial inflammatory hyperalgesia. Injection of complete Freund's adjuvant (CFA) into the upper lip/whisker pad of the rat produced significant and long-lasting thermal (> or =14 days) and mechanical (> or =28 days) hyperalgesia in the area of CFA injection. Both indomethacin and morphine, given systemically, significantly attenuated thermal hyperalgesia; the effect of morphine was shown to be opioid receptor-mediated. We also examined the contribution of the tetrodotoxin-resistant voltage-gated sodium channel Na(v)1.8 in CFA-produced orofacial mechanical hypersensitivity. Na(v)1.8 mRNA was increased > or =2.5-fold in trigeminal ganglion neurons 1 and 2 weeks after CFA treatment, and Na(v)1.8 protein was increased in the infraorbital nerve over a similar time course. The changes observed were time-dependent and had returned to baseline when examined 2 months after inflammation; there were no changes in Na(v)1.9 mRNA in trigeminal ganglion neurons after CFA treatment. In support of this, Na(v)1.8 antisense oligodeoxynucleotide treatment significantly attenuated CFA-produced mechanical hypersensitivity. These results document development of a model of inflammatory orofacial hyperalgesia, which, consistent with other reports, indicate a contribution of tetrodotoxin-resistant, voltage-gated sodium channel Na(v)1.8. ⋯ Orofacial hypersensitivity develops postoperatively as a routine course of orofacial surgery, and mechanical allodynia is characteristic of temporomandibular joint disorder. The results described in this report are novel with respect to the duration of orofacial hypersensitivity produced and suggest that pharmacological targeting of the voltage-gated sodium channel Na(v)1.8 may be useful in managing hypersensitivity.
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Review Case Reports
Perioperative pain management in the opioid-tolerant individual.
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The main aims of this work were to test the psychometric properties of the Catalan version of the Pain Catastrophizing Scale (PCS) and to assess the usefulness of the scale when used with whiplash patients. This article reports results from 2 complementary studies. In the first one, the PCS was administered to 280 students and 146 chronic pain patients to examine the psychometric properties of a new Catalan version of the instrument. A confirmatory factor analysis supported a second-order structure, in which 3 second-order factors (ie, rumination, helplessness, and magnification) load in a higher-order factor (ie, catastrophizing). The reliability of the Catalan version was supported by an acceptable internal consistency and test-retest values. Validity was supported by the correlations found among the PCS and pain intensity, pain interference, and depression. The objective of the second study was to evaluate the PCS when used with whiplash patients. In this second study, 141 patients with whiplash disorders participated. In general, the psychometric properties of the PCS were found appropriate, with factor analysis supporting the structure described in patients with chronic pain. Our data suggest that the PCS is a good instrument to assess catastrophic thinking in whiplash patients. ⋯ The usefulness of the PCS in whiplash disorders has been explored in this study. Results of our work show that the PCS can be a very useful tool to assess catastrophic thinking about pain in whiplash patients.
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Chronic low back pain (CLBP) is a prevalent pain condition associated with increased disability, lower quality of life, and poor relationship satisfaction. However, little research has examined the impact of the psychosocial environment in predicting relationship satisfaction among persons with CLBP. This study examined empirically supported psychosocial variables as potential mediators in the association between pain and relationship satisfaction. Patients with CLBP completed depression, partner support, pain, relationship satisfaction, pain catastrophizing, and pain-related fear measures (N = 54). Negative responses by a partner and depression were found to mediate the association between pain and relationship satisfaction, with negative responses emerging as the most important mediator. The current findings are consistent with a biopsychosocial framework of chronic pain and suggest that negative interpersonal interactions in patients with CLBP may be of central importance when considering psychosocial intervention. Theoretical and practical implications for treatment are discussed. ⋯ This study suggests that psychosocial variables, specifically depression and perceived negative partner responses, have a significant impact on relationship satisfaction among individuals with CLBP. These findings highlight issues integral to the social adjustment of patients with CLBP.
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Skeletal muscle injuries can induce chronic pain, but the underlying mechanism is unknown. One possible cause has been suggested to be an increased sensitivity to inflammatory mediators. We demonstrate that self-limited inflammatory hyperalgesia induced by intramuscular carrageenan (lasting approximately 5 days) results in a state of chronic-latent hyperalgesia, revealed by injection of prostaglandin E(2) (PGE(2)) 10 days after carrageenan at the same site. In carrageenan-pretreated muscle, PGE(2) produced hyperalgesia that was unattenuated even 14 days after injection, markedly longer than the 4-hour hyperalgesia induced by PGE(2) in naive rats. This chronic-latent hyperalgesia was reversed as well as prevented by spinal intrathecal injection of oligodeoxynucleotide antisense to protein kinase Cepsilon, a second messenger implicated in long-lasting plasticity in cutaneous nociceptors. ⋯ We describe a novel experimental model for chronic muscle pain, produced by mild acute muscle inflammation, that has clinical significance since it has the potential to reveal cellular processes by which acute inflammation or muscle trauma underlies chronic muscle pain.