Pain
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In animal models, allopregnanolone (ALLO) negatively modulates the hypothalamic-pituitary-adrenal (HPA) axis and has been shown to exert analgesic effects. The purpose of this study was to assess the relationship between plasma ALLO immunoreactivity (ALLO-ir), HPA-axis measures, and pain sensitivity in humans. Forty-five African Americans (21 men, 24 women) and 39 non-Hispanic Whites (20 men, 19 women) were tested for pain sensitivity to tourniquet ischemia, thermal heat, and cold pressor tests. ⋯ Also, only in the non-Hispanic Whites was cortisol associated with thermal heat tolerance (r=+.39, p<.05) and threshold (r=+.50, p<.01) and cold pressor tolerance (r=+.32, p<.05), and were beta-endorphin concentrations associated with cold pressor tolerance (r=+.33, p<.05). Mediational analyses revealed that higher cortisol levels mediated the relationship between lower ALLO-ir and increased thermal heat pain threshold in the non-Hispanic Whites only. These results suggest that lower ALLO-ir concentrations are associated with decreased pain sensitivity in humans, especially in non-Hispanic Whites, and that this relationship may be mediated by HPA-axis function.
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Randomized Controlled Trial Comparative Study
Comparison of general exercise, motor control exercise and spinal manipulative therapy for chronic low back pain: A randomized trial.
Practice guidelines recommend various types of exercise and manipulative therapy for chronic back pain but there have been few head-to-head comparisons of these interventions. We conducted a randomized controlled trial to compare effects of general exercise, motor control exercise and manipulative therapy on function and perceived effect of intervention in patients with chronic back pain. Two hundred and forty adults with non-specific low back pain 3months were allocated to groups that received 8weeks of general exercise, motor control exercise or spinal manipulative therapy. ⋯ The motor control exercise group had slightly better outcomes than the general exercise group at 8weeks (between-group difference: PSFS 2.9, 95% CI: 0.9-4.8; GPE 1.7, 95% CI: 0.9-2.4), as did the spinal manipulative therapy group (PSFS 2.3, 95% CI: 0.4-4.2; GPE 1.2, 95% CI: 0.4-2.0). The groups had similar outcomes at 6 and 12months. Motor control exercise and spinal manipulative therapy produce slightly better short-term function and perceptions of effect than general exercise, but not better medium or long-term effects, in patients with chronic non-specific back pain.
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The majority of research on pain catastrophizing has focused on its negative consequences for adjustment to chronic pain, with few investigations of factors that influence catastrophizing or its detrimental effects. Using a daily process methodology, the current study examined, first, the extent to which a supportive social environment plays a role in reduced catastrophizing, and second, the extent to which support might protect against the detrimental effects of catastrophizing on well-being. Sixty-nine married individuals with rheumatoid arthritis took part in an initial background interview, followed by twice daily telephone interviews (regarding pain intensity, negative affect, catastrophizing and satisfaction with spouse responses) for 1 week. ⋯ The relationship between pain and catastrophizing was attenuated in the context of increases in satisfaction with spouse responses. Negative affect was associated with increases in catastrophizing, but only when individuals reported decreases in satisfaction with spouse responses. Overall, findings were consistent with a model in which satisfaction with spouse responses serves as a coping resource, and suggests the importance of involving close others in treatments to reduce pain and catastrophizing.
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The perception of pain results from an interaction between nociceptive and antinociceptive mechanisms. A better understanding of the neural circuitry underlying these physiological interactions provides an important opportunity to develop better treatment strategies for and ultimately even prevent pain. Here, we investigated how repeated painful stimulation over several days is processed, perceived and finally modulated in the healthy human brain. ⋯ The decreased perception of pain over time is reflected in decreased BOLD responses to nociceptive stimuli in classical pain areas, including thalamus, insula, SII and the putamen. In contrast to this finding, we found that pain-related responses in the rACC, specifically the subgenual anterior cingulate cortex (sgACC), significantly increased over time. Given this area's predominant role in endogenous pain control, this response pattern suggests that habituation to pain is at least in part mediated by increased antinociceptive activity.
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Spinal glutamate transporters (GT) have been implicated in the mechanisms of neuropathic pain; however, how spinal GT uptake activity is regulated remains unclear. Here we show that alteration of spinal arachidonic acid (AA) turnover after peripheral nerve injury regulated regional GT uptake activity and glutamate homeostasis. Chronic constriction nerve injury (CCI) in rats significantly reduced spinal GT uptake activity ((3)H-glutamate uptake) with an associated increase in extracellular AA and glutamate concentration from spinal microdialysates on postoperative day 8. ⋯ Consistent with these findings, AACOCF3 reduced the development of both thermal hyperalgesia and mechanical allodynia, whereas diclofenac exacerbated thermal hyperalgesia, in CCI rats. Thus, spinal AA turnover may serve as a regulator in CCI-induced changes in regional GT uptake activity, glutamate homeostasis, and neuropathic pain behaviors. These data suggest that regulating spinal AA turnover may be a useful approach to improving the clinical management of neuropathic pain.