Pain
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The pain modulatory role of dopamine D2 receptors of the human forebrain was studied by determining the association between dopamine D2 receptor binding potential and the response to experimental pain. Nineteen healthy male volunteers participated in a dopamine D2 receptor positron emission tomography study. The extrastriatal regions of interest studied with [11C]FLB 457 as radioligand (n = 11) were the anterior cingulum, the medial and lateral thalamus, the medial and lateral frontal cortex, and the medial and lateral temporal cortex. ⋯ A psychophysical control study (n = 10) showed that cold pain responses were identical in the right and left hand. The results indicate that dopamine D2 receptor binding potential in the human forebrain, particularly in the striatum, may be an important parameter in determining the individual cold pain response and the potential for central pain modulation. Accordingly, an individual with only few available D2 receptors in the forebrain is likely to have a high tonic level of pain suppression, combined with a low capacity to recruit more (dopaminergic) central pain inhibition by noxious conditioning stimulation.
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Randomized Controlled Trial Clinical Trial
Anger and pain sensitivity in chronic low back pain patients and pain-free controls: the role of endogenous opioids.
The experience of anger (i.e. trait anger) and anger management style (i.e. anger-in, anger-out) are related to sensitivity to acute and chronic pain stimuli, although underlying mechanisms are unknown. This study tested whether anger variables are associated with impaired endogenous opioid antinociceptive activity, and whether these relationships differed between chronic pain patients and healthy normals. Forty-three chronic low back pain (LBP) sufferers and 45 pain-free normals received opioid blockade (8 mg naloxone i.v.) or placebo blockade (saline) in randomized, counterbalanced order in separate sessions. ⋯ Anger-out x LBP/normal interactions were non-significant, suggesting that links between anger-out and drug effects were similar for patients and normals. Controlling for depression did not eliminate the significant relationship between anger-out and drug effects. Findings suggest that anger-in and anger-out affect pain sensitivity through different mechanisms: only the effects of anger-out may be mediated by endogenous opioid dysfunction.
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Randomized Controlled Trial Clinical Trial
Immediate effects of dry needling and acupuncture at distant points in chronic neck pain: results of a randomized, double-blind, sham-controlled crossover trial.
To evaluate immediate effects of two different modes of acupuncture on motion-related pain and cervical spine mobility in chronic neck pain patients compared to a sham procedure. Thirty-six patients with chronic neck pain and limited cervical spine mobility participated in a prospective, randomized, double-blind, sham-controlled crossover trial. Every patient was treated once with needle acupuncture at distant points, dry needling (DN) of local myofascial trigger points and sham laser acupuncture (Sham). ⋯ For patient assessment of change, non-local acupuncture was significantly superior both to Sham (1.7 points; 95% CI 1.0, 2.5; P = 0.0001) and DN (1.5 points; 95% CI 0.4, 2.6; P = 0.008) but there was no difference between DN and Sham (0.1 point; 95% CI -1.0, 1.2; P = 0.8). Acupuncture is superior to Sham in improving motion-related pain and ROM following a single session of treatment in chronic neck pain patients. Acupuncture at distant points improves ROM more than DN; DN was ineffective for motion-related pain.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparative study of electronic vs. paper VAS ratings: a randomized, crossover trial using healthy volunteers.
The visual analogue scale (VAS) is an established, validated, self-report measure usually consisting of a 10 cm line on paper with verbal anchors labeling the ends. Palmtop computers (PTCs also known as personal digital appliances) have incorporated VAS entry by use of a touch screen. However, the validity and psychophysical properties of the electronic VAS have never been formally compared with the conventional paper VAS. ⋯ The median of correlations comparing eVAS and pVAS ratings was 0.99 for verbal stimuli and 0.98 for sensory stimuli. Multivariate analyses showed equivalent stimuli to be rated much the same whether entered on paper VAS or PTC touch screen VAS (P < 0.0001). Support was found for the validity of the computer version of the VAS scale.
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Randomized Controlled Trial Clinical Trial
Naloxone increases pain induced by topical capsaicin in healthy human volunteers.
Opioid receptors occur in locations of strategic importance within the central nervous system for modulation of pain. Is pain reduced by ongoing inhibition mediated by activation of these receptors? Experiments to date in which the opioid-receptor antagonist, naloxone, is administered during a painful event have yielded unclear results. Topically applied capsaicin can be used to induce tonic pain of moderate to severe intensity without tissue injury and is an ideal stimulus for studying acute pain modulation. ⋯ The naloxone induced a significant increase in pain compared both to baseline (P < 0.01) and placebo (P < 0.01). The peak effect, reached at 12-20 min after naloxone delivery, was 59% greater than placebo. This experiment suggests that acute pain is actively suppressed by endogenous opioid-receptor activation.