Pain
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Both trait anger-in (managing anger through suppression) and anger-out (managing anger through direct expression) are related to pain responsiveness, but only anger-out effects involve opioid mechanisms. Preliminary work suggested that the effects of anger-out on postoperative analgesic requirements were moderated by the A118G single nucleotide polymorphism of the mu opioid receptor gene. This study further explored these potential genotypexphenotype interactions as they impact acute pain sensitivity. ⋯ No genetic moderation was observed for anger-in, although significant main effects on MPQ-Affective ratings were noted (p<.005). Anger-in main effects were due to overlap with negative affect, but anger-outxA118G interactions were not, suggesting unique effects of expressive anger regulation. Results support opioid-related genotypexphenotype interactions involving trait anger-out.
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Deficient endogenous pain inhibition, e.g. Diffuse noxious inhibitory controls (DNIC), or hormonal abnormalities like hypocortisolism, could be responsible for chronic widespread pain in Chronic Fatigue Syndrome (CFS). Thirty-one CFS-patients with chronic pain and 31 healthy controls were subjected to spatial summation of thermal noxious stimuli by gradual immersion (ascending or descending) of the arm in warm water (46 degrees C). ⋯ In addition to the hyperalgesia in CFS, DNIC react slower to spatial summation of thermal noxious stimuli. We found no evidence for hypocortisolism in CFS, and the cortisol response to nociception was not different in CFS compared to healthy subjects. In conclusion, delayed pain inhibition may play a role in chronic widespread pain in CFS but further research is required.
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Previous studies have shown that peripheral nerve injury in rats induces increased expression of the voltage gated calcium channel (VGCC) alpha-2-delta-1 subunit (Ca v alpha2 delta1) in spinal dorsal horn and sensory neurons in dorsal root ganglia (DRG) that correlates to established neuropathic pain states. To determine if injury discharges trigger Ca v alpha2 delta1 induction that contributes to neuropathic pain initiation, we examined allodynia onset and Ca v alpha2 delta1 levels in DRG and spinal dorsal horn of spinal nerve ligated rats after blocking injury induced neural activity with a local brief application of lidocaine on spinal nerves before the ligation. The lidocaine pretreatment blocked ligation-induced discharges in a dose-dependent manner. ⋯ In addition, preemptive intrathecal Ca v alpha2 delta1 antisense treatments blocked concurrently injury-induced allodynia onset and Ca v alpha2 delta1 upregulation in dorsal spinal cord. These findings indicate that injury induced discharges regulate Ca v alpha2 delta1 expression in the spinal dorsal horn that is critical for neuropathic allodynia initiation. Thus, preemptive blockade of injury-induced neural activity or Ca v alpha2 delta1 upregulation may be a beneficial option in neuropathic pain management.
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Multicenter Study
Post-trauma ratings of pre-collision pain and psychological distress predict poor outcome following acute whiplash trauma: a 12-month follow-up study.
Patients with acute whiplash trauma were followed to examine if post-trauma ratings of pre-collision pain and psychological distress were associated with reduced work capability and neck pain at 12 months follow-up. The study included 740 consecutive patients (474 females, 266 males) referred from emergency departments or primary care after car accidents in four counties in Denmark. After the collision patients received a questionnaire on psychological distress, unspecified pain and socio-demographics and 12 months later a follow-up on work capability and neck pain was performed. ⋯ In conclusion unspecified as opposed to specified pain (neck pain) before the collision is associated with poor recovery and high accumulation of pre-collision psychological distress is associated with considerable neck pain at follow-up. However, no conclusions on causality can be drawn. Personal characteristics before the collision are important for recovery and attention to pre-collision characteristics may contribute to the prevention of poor recovery after acute whiplash trauma.