Pain
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Intradermal administration of low-molecular-weight hyaluronan (LMWH) in the hind paw induced dose-dependent (0.1, 1, or 10 µg) mechanical hyperalgesia of similar magnitude in male and female rats. However, the duration of LMWH hyperalgesia was greater in females. This sexual dimorphism was eliminated by bilateral ovariectomy and by intrathecal administration of an oligodeoxynucleotide (ODN) antisense to the G-protein-coupled estrogen receptor (GPR30) mRNA in females, indicating estrogen dependence. ⋯ Low-molecular-weight hyaluronan-induced hyperalgesia was significantly attenuated by pretreatment with high-molecular-weight hyaluronan (HMWH) in male, but not in female rats. After gonadectomy or treatment with ODN antisense to GPR30 expression in females, HMWH produced similar attenuation of LMWH-induced hyperalgesia to that seen in males. These experiments identify nociceptors at which LMWH acts to produce mechanical hyperalgesia, establishes estrogen dependence in the role of RHAMM in female rats, and establishes estrogen dependence in the inhibition of LMWH-induced hyperalgesia by HMWH.
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Sociodemographic inequalities in the occurrence of low back pain (LBP) are well-studied. This study aimed to examine complex sociodemographic inequalities in the risk of LBP consultation in the population from a socioeconomical intersectional perspective. Using register data, we identified 458,852 individuals aged 35 to 75 years residing in Skåne in 2013, with no previous LBP consultation since 2006. ⋯ The low DA of the intersectional strata indicates the existence of limited intersectional inequalities in LBP consultation. Therefore, interventions to reduce LBP risk should be universal rather than targeted to specific socioeconomic groups with a higher average risk. Before planning targeted intervention, other risk factors with higher DA need to be identified.
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In complex regional pain syndrome (CRPS), hyperalgesia encompasses uninjured sites on the ipsilateral side of the body and may also include the special senses because auditory discomfort often is greater on the CRPS-affected side. To determine whether this hemilateral hyperalgesia involves the visual system, the discomfort threshold to a light-source that increased in intensity at 100 lux/second from 500 to 3600 lux was investigated for each eye, and the nasal and temporal half of each visual field, in 33 patients with CRPS and 21 pain-free controls. Recent headache history was reviewed and, in patients with CRPS, sensitivity to mechanical and thermal stimuli was assessed in all 4 limbs and on each side of the forehead. ⋯ Similarly, mechanical and thermal hyperalgesia was greater in the CRPS-affected than contralateral limb and was greater ipsilateral than contralateral to CRPS in the forehead and nonsymptomatic limbs. Ipsilateral photophobia was associated with mechanical and thermal hyperalgesia in the ipsilateral forehead but not the CRPS-affected limb. Together, these findings suggest that aberrant processing of nociceptive input in the ipsilateral trigeminal-medullary region of the brainstem contributes to visual discomfort in CRPS.
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As a rite of passage to womanhood, 2 million girls undergo female genital circumcision (FGC)-the tradition of cutting, and often removing parts of the vulva-every year. The current study is the first to focus on the connection between peripheral nerve damage and chronic neuropathic pain in women with FGC. We used mixed methods-quantitative, qualitative, and physiological-to study chronic pain in Somali-Canadian women (N = 14). ⋯ Although they report good overall health and very low pain levels on the short form of the McGill Pain Questionnaire, pressure-pain quantitative sensory testing of the vulvar region applied through vulvalgesiometers shows pain thresholds consistent with those reported by women with chronic vulvar pain. Furthermore, qualitative interviews reveal a considerable amount of often debilitating pain in daily life. These results challenge the use of assessment tools offering elicited verbal pain language and highlight the importance of culturally sensitive ways of conceptualizing, measuring, and managing pain.
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Visceral pain is a prevalent symptom of inflammatory bowel disease that can be difficult to treat. Pain and hypersensitivity are mediated by extrinsic primary afferent neurons (ExPANs) that innervate the colon. Recent studies indicate that the colon epithelium contributes to initiating ExPAN firing and nociceptive responses. ⋯ We then investigated the effect of epithelial and ExPAN inhibition in the dextran sulfate sodium model of inflammatory bowel disease. Inhibition of the colon epithelium significantly decreased dextran sulfate sodium-induced hypersensitivity and was comparable with the inhibition of ExPANs. Together, these results reveal the potential of targeting the colon epithelium for the treatment of pain.