Pain
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Comparative Study
Self-medication of a cannabinoid CB2 agonist in an animal model of neuropathic pain.
Drug self-administration methods were used to test the hypothesis that rats would self-medicate with a cannabinoid CB(2) agonist to attenuate a neuropathic pain state. Self-medication of the CB(2) agonist (R,S)-AM1241, but not vehicle, attenuated mechanical hypersensitivity produced by spared nerve injury. Switching rats from (R,S)-AM1241 to vehicle self-administration also decreased lever responding in an extinction paradigm. (R,S)-AM1241 self-administration did not alter paw withdrawal thresholds in sham-operated or naive animals. ⋯ Our results suggest that cannabinoid CB(2) agonists may be exploited to treat neuropathic pain with limited drug abuse liability and central nervous system side effects. These studies validate the use of drug self-administration methods for identifying nonpsychotropic analgesics possessing limited abuse potential. These methods offer potential to elucidate novel analgesics that suppress spontaneous neuropathic pain that is not measured by traditional assessments of evoked pain.
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Recurrent joint bleedings in people with hemophilia (PWH) often progress into the full clinical picture of hemophilic arthropathy, accompanied by chronic pain. Although chronic pain is commonly present in PWH, investigations assessing pain thresholds have not been performed yet. Thus, the aim of this study was to obtain objective and subjective measures of joint pain in PWH and to relate these to the severity of joint pathology. ⋯ Interestingly, this increased pain sensitivity was related to the severity of clinical joint pathology. In addition, PWH reported their pain in a more descriptive and not affective manner and scored similar to controls in the mental domain of the SF-36, thereby indicating good coping strategies despite the chronic nature of their complaints. In conclusion, pain sensitivity at the site of the affected joints is increased and closely related to joint pathology in people with hemophilia.