Articles: hyperalgesia.
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Widespread pressure hyperalgesia, facilitated temporal summation of pain (TSP), and impaired conditioned pain modulation (CPM) have been found in knee osteoarthritis (KOA) patients compared with controls and these parameters have further been suggested to be altered in the elderly. This study investigated the influence of age on pressure hyperalgesia, TSP, and CPM in patients with KOA and controls. ⋯ Pressure hyperalgesia was affected by age whereas dynamic pain mechanisms such as TSP and CPM were unaffected suggesting that these parameters are robust for a larger age range and reliable for long-term follow-up studies.
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Objective Studies suggest that pain thresholds may be altered before and during migraine headaches, but it is still debated if a central or peripheral dysfunction is responsible for the onset of pain in migraine. The present blinded longitudinal study explores alterations in thermal pain thresholds and suprathreshold heat pain scores before, during, and after headache. Methods We measured pain thresholds to cold and heat, and pain scores to 30 seconds of suprathreshold heat four times in 49 migraineurs and once in 31 controls. ⋯ Conclusion Preictal heat hypoalgesia and reduced adaptation was followed by ictal trigeminal cold suballodynia and heat hyperalgesia. Our results support that cyclic alterations of pain perception occur late in the prodromal phase before headache. Further longitudinal investigation of how pain physiology changes within the migraine cycle is important to gain a more complete understanding of the pathogenic mechanisms behind the migraine attack.
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Skin biopsies from patients with neuropathic pain often show changes in epidermal innervation, although it remains to be elucidated to what extent such changes can be linked to a particular subgroup of nerve fibers and how these changes are correlated with pain intensity. Here, we investigated to what extent behavioral signs of hyperalgesia are correlated with immunohistochemical changes of peptidergic and non-peptidergic epidermal nerve fibers in a rat model of nerve injury-induced pain. Rats subjected to unilateral partial ligation of the sciatic nerve developed significant mechanical and thermal hyperalgesia as tested by the withdrawal responses of the ipsilateral footpad to von Frey hairs and hotplate stimulation. ⋯ In contrast, the expression of the P2X3 receptor, a marker for non-peptidergic nerve fibers, was not only significantly reduced but could also be correlated with behavioral hyperalgesia. When labeling both peptidergic and non-peptidergic nerve fibers with the pan-neuronal marker PGP9.5, the expression was significantly reduced, albeit without a significant correlation with behavioral hyperalgesia. In conjunction, our data suggest that the pathology of the P2X3 epidermal nerve fibers can be selectively linked to neuropathy, highlighting the possibility that it is the degeneration of these fibers that drives hyperalgesia.
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Cannabis and its psychoactive constituent Δ9-tetrahydrocannabinol (THC) have efficacy against neuropathic pain, however, this is hampered by their side effects. It has been suggested that co-administration with another major constituent cannabidiol (CBD) might enhance the analgesic actions of THC and minimise its deleterious side effects. We examined the basis for this phytocannabinoid interaction in a mouse chronic constriction injury (CCI) model of neuropathic pain. ⋯ Unlike THC, the low dose THC:CBD anti-allodynia was not cannabinoid receptor mediated. These findings demonstrate that CBD synergistically enhances the pain-relieving actions of THC in an animal neuropathic pain model, but has little impact on the THC-induced side effects. This suggests that low dose THC:CBD combination treatment has potential in the treatment of neuropathic pain.