Pain
-
Peripheral inflammation produces a long-lasting latent sensitization of spinal nociceptive neurons, that is, masked by tonic inhibitory controls. We explored mechanisms of latent sensitization with an established four-step approach: (1) induction of inflammation; (2) allow pain hypersensitivity to resolve; (3) interrogate latent sensitization with a channel blocker, mutant mouse, or receptor antagonist; and (4) disrupt compensatory inhibition with a receptor antagonist so as to reinstate pain hypersensitivity. We found that the neuropeptide Y Y1 receptor antagonist BIBO3304 reinstated pain hypersensitivity, indicative of an unmasking of latent sensitization. ⋯ We conclude that PKA and Epac are sufficient to maintain long-lasting latent sensitization of dorsal horn neurons that is kept in remission by the NPY-Y1 receptor system. Furthermore, we have identified and characterized 2 novel molecular signaling pathways in the dorsal horn that drive latent sensitization in the setting of chronic inflammatory pain: NMDAR→AC1→PKA→TRPA1/V1 and NMDAR→AC1→Epac1/2. New treatments for chronic inflammatory pain might either increase endogenous NPY analgesia or inhibit AC1, PKA, or Epac.
-
Randomized Controlled Trial
Somatosensory predictors of response to pregabalin in painful chemotherapy-induced peripheral neuropathy: a randomized, placebo-controlled, crossover study.
Painful chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating and treatment-resistant sequela of many chemotherapeutic medications. Ligands of α2δ subunits of voltage-gated Ca channels, such as pregabalin, have shown efficacy in reducing mechanical sensitivity in animal models of neuropathic pain. In addition, some data suggest that pregabalin may be more efficacious in relieving neuropathic pain in subjects with increased sensitivity to pinprick. ⋯ There was no significant difference between pregabalin and placebo in reducing average daily pain (22.5% vs 10.7%, P = 0.23) or worst pain (29.2% vs 16.0%, P = 0.13) from baseline. Post hoc analysis of patients with CIPN caused by oxaliplatin (n = 18) demonstrated a larger reduction in worst pain with pregabalin than with placebo (35.4% vs 14.6%, P = 0.04). In summary, baseline mechanical pain threshold tested on dorsal feet did not meaningfully predict the analgesic response to pregabalin in painful CIPN.
-
Randomized Controlled Trial Multicenter Study Comparative Study
Efficacy of a transdiagnostic emotion-focused exposure treatment for chronic pain patients with comorbid anxiety and depression: a randomized controlled trial.
The comorbidity between chronic pain and emotional problems has proven difficult to address with current treatment options. This study addresses the efficacy of a transdiagnostic emotion-focused exposure treatment ("hybrid") for chronic pain patients with comorbid emotional problems. Adults (n = 115) with chronic musculoskeletal pain and functional and emotional problems were included in a 2-centre, parallel randomized controlled, open-label trial comparing this treatment to an active control condition receiving a guided Internet-delivered pain management treatment based on CBT principles (iCBT). ⋯ There were no differences on anxiety and pain intensity. Observed proportions of clinically significant improvement favoured the hybrid on all but one comparison, but no statistically significant differences were observed. We conclude that the hybrid emotion-focused treatment may be considered an acceptable, credible, and efficacious treatment option for chronic pain patients with comorbid emotional problems.
-
Randomized Controlled Trial
Cortisol affects pain sensitivity and pain-related emotional learning in experimental visceral but not somatic pain: a randomized controlled study in healthy men and women.
Despite growing interest in the role of stress mediators in pain chronicity, the effects of the stress hormone cortisol on acute pain remain incompletely understood. In a randomized, double-blind, placebo-controlled study with N = 100 healthy volunteers, we tested the effects of oral hydrocortisone (20 mg) in 2 widely used pain models for the visceral and somatic modality. Salivary cortisol was increased in the hydrocortisone group (time × group: P < 0.001). ⋯ Conditioned pain-related fear in response to predictive cues was only observed for the visceral modality (time × modality: P = 0.026), an effect that was significantly reduced by hydrocortisone compared with placebo (time × group: P = 0.028). This is the first psychopharmacological study to support that acutely increased cortisol enhances pain sensitivity and impairs pain-related emotional learning within the visceral, but not the somatic pain modality. Stress-induced visceral hyperalgesia and deficits in emotional pain-related learning could play a role in the pathophysiology of chronic visceral pain.