Articles: hyperalgesia.
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Pregabalin is used for treatment of neuropathic pain conditions. The present study evaluated effects of pregabalin in 2 rat models of muscle-induced hyperalgesia: Inflammatory and noninflammatory. Muscle hyperalgesia (withdrawal threshold to compression of the muscle) and cutaneous hyperalgesia of the paw (withdrawal threshold to von Frey filaments) were measured before and after induction of hyperalgesia and after treatment with pregabalin (saline, 10 to 100 mg/kg i.p.). In the inflammatory model, 3% carrageenan injected into 1 gastrocnemius muscle decreased the mechanical withdrawal threshold of the paw bilaterally and the compression withdrawal threshold of the muscle ipsilaterally 2 weeks later. Pregabalin (10 to 100 mg/kg) increased the compression withdrawal threshold of the inflamed muscle when compared with vehicle controls. Pregabalin also increased the mechanical withdrawal threshold of the paw bilaterally, but only with 100 mg/kg. In the noninflammatory model, 2 unilateral injections of acidic saline into the gastrocnemius muscle produced bilateral cutaneous and muscle hyperalgesia 24 hours after the second injection. Pregabalin (10 to 100 mg/kg i.p.) significantly increased the compression withdrawal thresholds of the muscle and the mechanical withdrawal threshold of the paw bilaterally when compared with vehicle. However, pregabalin also has significant motor effects at the higher doses (60 to 100 mg/kg). Therefore, pregabalin reduces both muscle and cutaneous hyperalgesia that occurs after muscle insult in 2 animal models of muscle pain at doses that do not produce ataxia. ⋯ This study shows that pregabalin reduces both cutaneous and muscle hyperalgesia in inflammatory and noninflammatory models of muscle pain. Thus, pregabalin may be an effective treatment for people with chronic muscle pain.
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About 60% of patients complain of cutaneous allodynia during migraine episodes, often in the periorbitary region of the pain side. Pre-clinical studies have shown that the underlying mechanism is sensitisation of primary nociceptors and central trigeminovascular neurons and that patients have a lower pain threshold for mechanical stimulation compared to controls. The objective of this study was to determine the prevalence of allodynia during headache attacks in different forms of migraine. ⋯ Allodynia was a common complaint in migraineurs, being present in more than 40% patients of each group. A higher frequency was observed in MA and in CM patients. This observation may suggest that both frequency of attacks and presence of aura episodes may contribute to induce changes in neuronal activation threshold thought to sustain allodynia.
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Transient receptor potential vanilloid (TRPV)1 is a ligand-gated cation channel expressed by primary sensory neurons, including those in the dorsal root ganglia (DRG). TRPV1 plays an essential role in development of inflammatory thermal hyperalgesia after tissue injury and its expression in rat lumbar DRG is increased after hindpaw inflammation. However, the identity of factors mediating forepaw inflammatory hyperalgesia has remained elusive. ⋯ Paratracheal injection of short interfering RNA targeting TRPV1 blocked TRPV1 up-regulation in cervical DRG and abolished inflammation-mediated HPL reductions seen at 50 degrees C. However, thermal hyperalgesia previously established by inflammation was not reversed by short interfering RNA injection. These results indicate that: (i) enhanced TRPV1 expression in cervical DRG is closely associated with development of inflammatory thermal hyperalgesia in the forepaw after tissue injury and (ii) RNA interference targeting TRPV1 prevents inflammatory thermal hyperalgesia after forepaw injuries but does not ameliorate it when already established in a rat model of nociceptive pain representing upper limb injury in humans.
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Studies in vitro suggest that the standardised extract of Ginkgo biloba, EGb-761 has anti-inflammatory properties and modulatory effects on key pain-related molecules. This study investigated the analgesic and anti-inflammatory effects of EGb-761 on carrageenan-induced inflammatory and hindpaw incisional pain. ⋯ EGb-761 dose-dependently alleviates acute inflammatory and surgically induced thermal hyperalgesia and is comparable to diclofenac, a commonly prescribed non-steroidal anti-inflammatory drug. This indicates that EGb-761 has analgesic potential in acute inflammatory pain.