The journal of pain : official journal of the American Pain Society
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Emotional regulation is an important variable in the experience of pain. Currently, there are no experimental investigations of the relation between emotional regulation and pain. The goal of the present study work was to analyze differences in pain perception and mood generated by the cold-pressor (CPT) experimental paradigm in women with high and low emotional regulation. Two groups of women were formed as a function of their level of emotional regulation: women with high emotional repair (N = 24) and women with low emotional repair (N = 28), all of whom performed the CPT. The results show that the women with a high score in emotional repair reported having experienced less sensory pain and affective pain during the immersion, as well as a more positive affective state before beginning the task. During the experimental task, they also reported a better mood, thus displaying lower impact of the experience of pain. ⋯ Emotional regulation is proposed as a key element to manage the emotional reaction that accompanies the experience of acute pain experimentally induced by the CPT experimental paradigm in a sample of healthy women.
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Clinical and preclinical data concur that sleep disruption causes hyperalgesia, but the brain mechanisms through which sleep and pain interact remain poorly understood. Evidence that pontine components of the ascending reticular activating system modulate sleep and nociception encouraged the present study testing the hypothesis that hypocretin-1 (orexin-A) and an adenosine receptor agonist administered into the pontine reticular nucleus, oral part (PnO) each alter thermal nociception. Adult male rats (n = 23) were implanted with microinjection guide tubes aimed for the PnO. The PnO was microinjected with saline (control), hypocretin-1, the adenosine A(1) receptor agonist N(6)-p-sulfophenyladenosine (SPA), the hypocretin receptor-1 antagonist N-(2-Methyl-6-benzoxazolyl)-N''-1,5-naphthyridin-4-yl-urea (SB-334867), and hypocretin-1 plus SB-334867. As an index of antinociceptive behavior, the latency (in seconds) to paw withdrawal away from a thermal stimulus was measured following each microinjection. Compared to control, antinociception was significantly increased by hypocretin-1 and by SPA. SB-334867 increased nociceptive responsiveness, and administration of hypocretin-1 plus SB-334867 blocked the antinociception caused by hypocretin-1. These results suggest for the first time that hypocretin receptors in rat PnO modulate nociception. ⋯ Widely distributed and overlapping neural networks regulate states of sleep and pain. Specifying the brain regions and neurotransmitters through which pain and sleep interact is an essential step for developing adjunctive therapies that diminish pain without disrupting states of sleep and wakefulness.
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Randomized Controlled Trial Clinical Trial
The impact of placebo, psychopathology, and expectations on the response to acupuncture needling in patients with chronic low back pain.
Comorbid psychopathology is a variable not explored in the acupuncture RCTs that could explain whether subgroups of patients with chronic low back pain have differential responses to acupuncture or placebo treatments. This was a controlled, blinded, crossover trial of verum acupuncture and validated sham acupuncture in 40 CLBP patients, with a Low or High level of psychiatric comorbidity. They completed a 0 to 10 rating scale for pain at the beginning and end of each treatment session, and rated their expectations for change in pain. Verum acupuncture was performed at Large Intestine 4 on the dorsal right hand for 30 minutes by a licensed acupuncturist. Data analysis used percent improvement in pain as the primary outcome for each of the treatment sessions. Both groups (21 Low and 19 High) reported significant analgesia with verum acupuncture needling, mean 33%, P = .9 for difference between groups; and with placebo, 26%, P = .09. In both groups, expectations were only a significant predictor of verum acupuncture response, P = .002, such that those with greater expectations had greater pain relief. Psychiatric comorbidity does not significantly impact acupuncture or placebo acupuncture analgesia in CLBP. It does not affect the positive impact of expectations on reported pain relief from real acupuncture. ⋯ Psychiatric comorbidity may predict differences between acupuncture and placebo responses, not otherwise seen in the RCTs for low back pain. Using a blinded, crossover design, we report that it does not predict outcome, nor does it seem to modify the effect of expectancy (a known predictor) on acupuncture response.
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This study compared recalled average pain, assessed at the end of the day, with the average of real-time pain ratings recorded throughout the day among patients with osteoarthritis (OA). Participants (N = 157) with hand, hip, or knee OA completed electronic pain diaries on 1 weekend day and 1 weekday. Diaries included at least 7 pain ratings per day, immediately after waking and every 2 hours following, using a visual analog scale (VAS) scored as 1 to 100 (scores not seen by participants). At the end of each diary day, participants rated their average pain that day on the same VAS. Pearson correlations examined associations between recalled average pain and the average of real-time pain ratings that day. Mixed models, including interaction terms, examined whether associations between recalled and actual average pain ratings differed according to the following patient characteristics: joint site, age, race, gender, study enrollment site, and pain catastrophizing. Correlations between recalled and actual average pain ratings were r = .88 for weekdays and r = .86 for weekends (P < .0001). In mixed models, there were no significant interaction terms for any patient characteristics. In summary, patients with OA accurately recalled their average pain over a 1-day period, and this did not differ according to any patient characteristics examined. ⋯ This study showed that patients with OA accurately recalled their average pain over a single-day period, and this did not differ according to patient characteristics. Results of this study indicate that end-of-day recall is a practical and valid method for assessing patients' average pain during a day.
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Peripheral nerve injury leads to neuropathic pain, but the underlying mechanisms are not clear. The TRPV1 channel expressed by nociceptors is one receptor for noxious heat and inflammatory molecules. Lumbar 4 (L4) spinal nerve ligation (SNL) in mice induced persistent heat hyperalgesia 4 to 10 days after injury. The heat hypersensitivity was completely reversed by the TRPV1 antagonist A-425619. Furthermore, DRG neurons were isolated from the injured L4 ganglia or adjacent L3 ganglia 4 to 10 days after L4 SNL. Whole-cell patch-clamp recordings were performed and heat stimuli (22 degrees C to 50 degrees C/3 s) were applied to the soma. Neurons were classified by soma size and isolectin-B4 (IB4) binding. Among directly injured L4 neurons, SNL increased the percentage of small-diameter IB4-positive neurons that were heat-sensitive from 13% (naive controls) to 56% and conversely decreased the proportion of small IB4-negative neurons that were heat-sensitive from 66% (naive controls) to 34%. There was no change in IB4 binding in neurons from the injured ganglia. Surprisingly, in neurons from the adjacent L3 ganglia, SNL had no effect on the heat responsiveness of either IB4-positive or negative small neurons. Also, SNL had no effect on heat responses in medium-large-diameter neurons from either the injured or adjacent ganglia. ⋯ TRPV1 function is upregulated in IB4-positive sensory neurons, and TRPV1 is responsible for the behavioral heat hypersensitivity in the spinal nerve ligation model. Because IB4-positive neurons may contribute to the emotional perception of pain, TRPV1 antagonists, targeting both sensory and affective pain components, could have broad analgesic effects.