Pain
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Headaches can be evoked by activation of meningeal nociceptors, but an involvement of pericranial tissues is debated. We aimed to examine a possible extracranial innervation by meningeal afferents in the rat. For in vivo neuronal tracing, dextran amines were applied to the periosteum underlying the temporal muscle. ⋯ Noxious stimulation of the temporal muscle caused CGRP release from the dura mater and elevated meningeal blood flow. Collaterals of meningeal nerve fibers project through the skull, forming functional connections between extra- and intracranial tissues. This finding offers a new explanation of how noxious stimulation of pericranial tissues can directly influence meningeal nociception associated with headache generation and why manual therapies of pericranial muscles may be useful in headaches.
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Cannabinoid agonists such as Δ(9)-tetrahydrocannabinol (THC) are more potent and/or efficacious antinociceptive agents in female than male rats using acute pain models. We tested the hypothesis that THC is more effective in females than males using a model of longer-lasting, inflammatory pain. THC's anti-allodynic, anti-hyperalgesic, and anti-edema effects were examined 1, 3, and 7 days after injection of complete Freund's adjuvant (CFA) into the hind paw. ⋯ THC's anti-edema effect in males. This study suggests that cannabinoids may be better at reducing edema in males while being more effective against inflammatory pain in females. Furthermore, sex differences in THC's peripheral effects against inflammatory pain may be a result of activation of both types of cannabinoid receptors in females, in contrast to predominantly CB1 receptors in males.
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Although chronic pain has been linked to poorer psychosocial well-being in the spouse, the extent to which patient pain affects spouse sleep is unknown. The aim of the present study was to test the hypothesis that greater daily knee pain would be associated with poorer sleep for the spouse that evening. We also tested the hypothesis that this pain contagion is exacerbated in couples who have a close relationship. ⋯ The effects of patient pain on spouse sleep were not due to disturbances in patient sleep and were also independent of spouse sex, depressive symptoms, and physical comorbidities; both partners' negative affect; and the quality of marital interactions throughout the day. As predicted, we also found that patient pain was more strongly related to less refreshing sleep for spouses who were in a close relationship. Findings illustrate that chronic pain may place the spouse's health at risk and suggest an important target for couple-oriented interventions.
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Randomized Controlled Trial
Specifying the nonspecific components of acupuncture analgesia.
It is well known that acupuncture has pain-relieving effects, but the contribution of specific and especially nonspecific factors to acupuncture analgesia is less clear. One hundred one patients who developed pain of ≥ 3 on a visual analog scale (VAS, 0 to 10) after third molar surgery were randomized to receive active acupuncture, placebo acupuncture, or no treatment for 30 min with acupuncture needles with potential for double-blinding. Patients' perception of the treatment (active or placebo) and expected pain levels (VAS) were assessed before and halfway through the treatment. ⋯ Expected pain levels accounted for significant and progressively larger amounts of the variance in pain ratings after both active and placebo acupuncture (up to 69.8%). This is the first study to show that under optimized blinding conditions, nonspecific factors such as patients' perception of and expectations toward treatment are central to the efficacy of acupuncture analgesia and that these factors may contribute to self-reinforcing effects in acupuncture treatment. To obtain an effect of acupuncture in clinical practice, it may therefore be important to incorporate and optimize these factors.