Pain
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Ingestion of monosodium glutamate (MSG) causes headache, nausea, and craniofacial tenderness in healthy individuals. The present study explored whether MSG produces behavioural signs of headache, nausea, and changes in craniofacial sensitivity in rats. The behavior of male and female Sprague-Dawley rats was video recorded before and after intraperitoneal (i.p.) injections of MSG (1-1000 mg/kg), nitroglycerin (GTN, 10 mg/kg), or normal saline. ⋯ Co-administration of sumatriptan or naproxen with MSG (1000 mg/kg) significantly attenuated MSG-induced nocifensive and headache-like behaviors. Our data suggest that systemic administration of MSG to rats induces behavioral correlates of headache and nausea. This model may offer another avenue for research on the mechanism and treatment of primary headache disorders such as migraine.
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The traditional construct of acute pain vs chronic pain is arbitrary and obscures fundamental differences in clinical pain phenomena. A more powerful dichotomy between peripherally generated pain and centrally maintained pains can facilitate advances in both pain research and clinical care. We should abandon the temporally based pain classification scheme because it does not accurately reflect the underlying principles inherent in the phenomena of pain.