Pain
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Behavioral and neurochemical studies have shown that the coeruleospinal modulation system is activated by peripheral inflammation, and that this modulation system is active in only the dorsal horn ipsilateral, but not in the dorsal horn contralateral, to the site of inflammation; the present study was designed to confirm electrophysiologically this previous finding. Extracellular recordings from dorsal horn neurons were continued for at least 4 h after the induction of inflammation. Unilateral hindpaw inflammation was produced by a subcutaneous injection of carrageenan (2 mg in 0.15 ml saline). ⋯ Four hours after the induction of inflammation, there was a significant increase in both the background activity and heat-evoked response in neurons in LC/SC-lesioned compared to LC/SC-intact rats. In neurons located in the dorsal horn contralateral to the inflamed paw, 4 h after inflammation, no significant increase in either the background activity or the heat-evoked response in neurons in LC/SC-lesioned rats was observed, as well as in the case before inflammation. These results suggest that the coeruleospinal modulation system is active in only the dorsal horn ipsilateral, but not in the dorsal horn contralateral, to the site of inflammation during the development of unilateral hindpaw inflammation.
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Randomized Controlled Trial Multicenter Study Comparative Study Clinical Trial
Tramadol in post-herpetic neuralgia: a randomized, double-blind, placebo-controlled trial.
The efficacy and safety of sustained-release tramadol compared to placebo in the treatment of post-herpetic neuralgia were evaluated in a multicenter, randomized, double-blind, parallel-group study in 127 outpatients. Treatment was administrated for 6 weeks. The dose of tramadol could be increased from 100 mg/day to 400 mg/day (300 mg/day in patients more than 75 years old). ⋯ Tramadol was administered at an average dosage of 275.5 (89.7) mg/day after a 1-week dose-adaptation period. Tramadol was well tolerated. No notable difference appeared between groups either in the percentage of patients with treatment-associated adverse events (TAAE) (29.7% in the tramadol group and 31.8% in the placebo group) or in the total number of TAAE (31 in the tramadol group and 28 in the placebo group).
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Randomized Controlled Trial Clinical Trial
Injection of nerve growth factor into human masseter muscle evokes long-lasting mechanical allodynia and hyperalgesia.
Nerve growth factor (NGF) is a neurotrophic protein with a pivotal role in development and maintenance of the nervous system on one side and inflammatory and neuropathic pain states on the other. NGF causes clear signs of behavioral hyperalgesia in animal models and following intradermal and systemic administration in humans. The present double-blinded, placebo-controlled study was designed to test quantitatively the effect and duration (1h, 1, 7, 14, 21 and 28 days) of NGF (5 microg in 0.2 ml) injected into the masseter muscle. ⋯ Systemic adverse effects were noted in one subject who reported fever and slight discomfort about 8h after the NGF injection. In conclusion, this is the first study to show that injection of NGF into the human masseter muscle causes local signs of mechanical allodynia and hyperalgesia that persist for at least 7 days as well as pain during strenuous jaw movement. The present pain model is safe and may be used to gain further insight into the neurobiological mechanisms of muscle pain and sensitization.
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Randomized Controlled Trial Comparative Study Clinical Trial
Intra-articular (IA) catheter administration of postoperative analgesics. A new trial design allows evaluation of baseline pain, demonstrates large variation in need of analgesics, and finds no analgesic effect of IA ketamine compared with IA saline.
All previous studies of intra-articular (IA) analgesic drugs for postarthroscopy pain have administered test-drugs at the end of the arthroscopic procedure, before any baseline pain could be assessed. Assay sensitivity has often not been documented or has been assumed to be present if a placebo control group had significant pain during the observation period. We present an improved study design employing an IA catheter for test-drug administration only in patients with moderate-to-severe baseline pain within 2h postoperatively. ⋯ The new method for IA analgesic trials solves the problem with undesirable inclusion of patients with no or mild pain. We observed rapid onset and significant pain relief after IA injection of 10 ml saline with or without ketamine 10mg, but no difference between these two test medications. Intra-muscular ketamine 10mg showed significantly better early pain relief, global evaluation, and longer time to rescue analgesic, compared with IA ketamine 10mg.
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Randomized Controlled Trial Clinical Trial
Gut pain and hyperalgesia induced by capsaicin: a human experimental model.
Human experimental visceral pain models using chemical stimulation are needed for the study of visceral hyperexcitability. Our aim was to stimulate the human gut with chemical activators (capsaicin, glycerol) and measure quantitatively the induced hyperexcitability to painful mechanical gut distension. Ten otherwise healthy subjects with an ileostoma participated. ⋯ No significant manifestations were found after application of glycerol and saline. Application of capsaicin to the human ileum induces pain and mechanical hyperalgesia. Specific activation of nociceptors in the gut mucosa provides new possibilities to study clinical relevant visceral pain mechanisms.