Pain
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The role of peroxynitrite (PN) as a mediator of nociceptive signaling is emerging. We recently reported that the development of central sensitization that follows the intraplantar injection of carrageenan in rats is associated with spinal PN synthesis. We now demonstrate that a significant pathway through which spinal PN modulates central sensitization is post-translational tyrosine nitration of key proteins involved in the glutamatergic pathway, namely glutamate transporter GLT-1 and glutamine synthetase (GS). ⋯ Carrageenan-induced hyperalgesia was also associated with nitration and inactivation of spinal mitochondrial superoxide dismutase (MnSOD) known to provide a critical source of PN during central sensitization. Nitration of GLT-1 and GS contributes to central sensitization by enhancing glutamatergic neurotransmission. Our results support the critical role of nitroxidative stress in the development of hyperalgesia and suggest that post-translational nitration of enzymes and transporters linked to glutamatergic neurotransmission represent a novel mechanism of central sensitization.
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Dyspnea and pain have a number of similarities. Recent brain imaging experiments showed that similar cortical regions are activated by the perceptions of dyspnea and pain. We tested the hypothesis that an individual's pain sensitivity might parallel the individual's dyspnea sensitivity. ⋯ A significant correlation was observed between the pain threshold time and the period of no respiratory sensation in both the PT and PS groups. However, no significant association was observed between pain and dyspnea tolerance in both groups. In conclusion, an individual's pain threshold is correlated to the individual's dyspnea threshold, but the individual's pain tolerance is not consistently correlated to the individual's dyspnea tolerance.
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The objective was to compare the Severity of Dependence Scale (SDS) score and pattern of medication use in persons with secondary chronic headache (>or= 15 days/month for at least 3 months) in a cross-sectional epidemiological survey. A posted questionnaire screened for chronic headache. Neurological residents interviewed those with self-reported chronic headache. ⋯ The sensitivity, specificity, positive and negative predictive values were 0.82, 0.82, 0.82 and 0.83, respectively. Thus the SDS score correlates with medication overuse, and a high SDS score suggests dependency-like behaviour in persons with secondary chronic headache. The use of SDS score in subjects with frequent pain episodes may contribute to the detection of medication overuse and better management of this group of patients.