Pain
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Randomized Controlled Trial
Repetitive Transcranial Magnetic Stimulation Induced Analgesia Depends on N-Methyl-D-Aspartate Glutamate Receptors.
We investigated the role of glutamate N-methyl-d-aspartate (NMDA) receptors in the analgesic effects induced by repetitive transcranial magnetic stimulation (rTMS). In a randomized, double-blind, crossover study, we compared the effects of ketamine and placebo on the analgesic effects of motor cortex (M1) or dorsolateral prefrontal cortex/premotor cortex (DLPFC/PMC) stimulation. Three groups of 12 healthy volunteers underwent active rTMS (10Hz, 80% resting motor threshold, 1,500 pulses per session) of the right M1, active stimulation of the right DLPFC/PMC, or sham stimulation during 2 experimental sessions 2 weeks apart. ⋯ Ketamine injection significantly decreased the analgesic effects of both M1 and DLPFC/PMC stimulation. The decrease in the analgesic effect of rTMS was not associated with changes in cortical excitability parameters, which were not influenced by rTMS following the administration of either saline or ketamine. Thus, rTMS-induced analgesia depends on glutamate NMDA receptors and may involve long-term potentiation-like mechanisms.
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Review Comparative Study
A Comparison of the Clinical and Experimental Characteristics of Four Acute Surgical Pain Models: Dental Extraction, Bunionectomy, Joint Replacement and Soft Tissue Surgery.
When a clinical trial of an analgesic produces a negative finding, it is important to consider the influence (if any) of experimental error on the validity of that result. Although efforts to identify and minimize experimental error in chronic pain investigations have begun in earnest, less work has been performed on the optimization of acute pain methodology. Of the acute surgical pain methodology articles that have been published over the last decade, almost all focus on either the dental or bunion model. ⋯ The purposes of this review were (1) to qualitatively describe the clinical and experimental characteristics of the 4 classic surgical models: dental extraction, bunionectomy, joint replacement, and soft tissue surgery; and (2) to quantitatively compare the models by analyzing 3 factors: effect size, enrollment rate, and demographics. We found that the dental extraction and bunionectomy models had higher assay sensitivity than the joint replacement and soft tissue surgery models. It is probable that this finding is secondary to the superior experimental conditions under which the dental and bunion models are executed (utilization of few centers that have the ability to reduce surgical, anesthetic, and postoperative confounders).