Pain
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Clinical Trial
White matter integrity of the descending pain modulatory system is associated with interindividual differences in placebo analgesia.
The ability for endogenous pain control varies considerably among individuals. The mechanisms underlying this interindividual difference are incompletely understood. We used placebo analgesia as a classic model of endogenous pain modulation in combination with diffusion tensor magnetic resonance imaging to test the hypothesis of a structural predisposition for the individual capacity of endogenous pain control. ⋯ The individual placebo analgesic effect was positively correlated with FA in the right dorsolateral prefrontal cortex, left rostral anterior cingulate cortex, and the periaqueductal grey. Probabilistic tractography seeded in these regions showed that stronger placebo analgesic responses were associated with increased mean fractional anisotropy values within white matter tracts connecting the periaqueductal grey with pain control regions such as the rostral anterior cingulate cortex and the dorsolateral prefrontal cortex. Our findings provide the first evidence that the white matter integrity within and between regions of the descending pain modulatory network is critically linked with the individual ability for endogenous pain control.
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Comparative Study
Effects of gonadal hormones on the peripheral cannabinoid receptor 1 (CB1R) system under a myositis condition in rats.
In this study, we assessed the effects of peripherally administered cannabinoids in an orofacial myositis model, and the role of sex hormones in cannabinoid receptor (CBR) expression in trigeminal ganglia (TG). Peripherally administered arachidonylcyclopropylamide (ACPA), a specific CB1R agonist, significantly attenuated complete Freund's adjuvant (CFA)-induced mechanical hypersensitivity in the masseter muscle in male rats. The ACPA effect was blocked by a local administration of AM251, a specific CB1R antagonist, but not by AM630, a specific CB2R antagonist. ⋯ The cytokines did not alter the CB1R mRNA level in TG from intact as well as ovariectomized female rats. Neither estradiol supplement nor estrogen receptor blockade had any effects on CB1R expression. These data indicate that testosterone, but not estradiol, is required for the regulation of CB1Rs in TG under inflammatory conditions, which provide explanations for the sex differences in the antihyperalgesic effects of peripherally administered cannabinoids.
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Comparative Study
Differential effects of left/right neuropathy on rats' anxiety and cognitive behavior.
Chronic pain is frequently accompanied by a deterioration of emotional behavior and cognitive function. A small number of studies in humans concluded that pain-associated negative affect is more pronounced when pain is localized in the left side of the body. It has been suggested that such side bias results from cortical function lateralization. ⋯ On the contrary, SNI-R animals presented cognitive deficits in all tasks except in the reference memory, but displayed a normal anxiety-like profile. Our results show that left- and right-sided neuropathic pain differentially affects emotional behavior, which is in accordance with previous observations in human subjects, both in experimentally induced pain and in chronic pain conditions. Additionally, our results demonstrate that the cognitive function deterioration associated with unilateral neuropathic chronic pain conditions is also differentially affected.
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Review Comparative Study
No additional value of fusion techniques on anterior discectomy for neck pain: a systematic review.
We aimed to assess the effects of additional fusion on surgical interventions to the cervical spine for patients with neck pain with or without radiculopathy or myelopathy by performing a systematic review. The search strategy outlined by the Cochrane Back Review Group (CBRG) was followed. The primary search was conducted in MEDLINE, EMBASE, CINAHL, CENTRAL and PEDro up to June 2011. ⋯ Results revealed no clinically relevant differences in recovery: the pooled risk difference in the short-term follow-up was -0.06 (95% confidence interval -0.22 to 0.10) and -0.07 (95% confidence interval -0.14 to 0.00) in the long-term follow-up. Pooled risk differences for pain and return to work all demonstrated no differences. There is no additional benefit of fusion techniques applied within an anterior discectomy procedure on pain, recovery and return to work.