Pain
-
Although N-methyl-d-aspartate (NMDA) receptor antagonists potentiate antinociceptive effects induced by various exogenous opioids at the spinal, supraspinal, or peripheral level, less is known regarding the interaction between NMDA and endogenous opioids in antinociception. We therefore assessed the effects of NMDA receptor antagonists on endogenous opioids in antinociception at the peripheral level by testing the ability of the locally administered receptor antagonists to modify pain-related behavior induced by carrageenan injection into the knee joint. The NMDA receptor antagonist AP-5 or the exogenous opioid morphine was injected intra-articularly before carrageenan injection and 5h after carrageenan injection, respectively. ⋯ Intriguingly, injection of naloxone 5h after carrageenan injection reversed the antinociceptive effects of AP-5 pre-treatment, although naloxone alone had no effect on carrageenan-induced pain-related behavior. Western blots showed that AP-5 pre-treatment followed by carrageenan injection resulted in a higher level of beta-endorphin protein in the DRG and saphenous nerve, but not in the synovial membrane, than that observed following saline control treatment. These results suggest that inhibition of the NMDA receptor unmasks antinociception induced by endogenous opioids at the peripheral level, partly through the increased protein level of the endogenous mu-opioid peptide beta-endorphin in DRG and saphenous nerve.
-
Review Meta Analysis
How effective are patient-based educational interventions in the management of cancer pain? Systematic review and meta-analysis.
This review aimed to quantify the benefit of patient-based educational interventions in the management of cancer pain. We undertook a systematic review and meta-analysis of experimentally randomised and non-randomised controlled clinical trials identified from six databases from inception to November 2007. Two reviewers independently selected trials comparing intervention (formal instruction on cancer pain and analgesia on an individual basis using any medium) to usual care or other control in adults with cancer pain. ⋯ Compared to usual care or control, educational interventions improved knowledge and attitudes by half a point on 0-5 rating scale (weighted mean difference 0.52, 95% confidence interval 0.04-1.0), reduced average pain intensity by over one point on 0-10 rating scale (WMD -1.1, -1.8 to -0.41) and reduced worst pain intensity by just under one point (WMD -0.78, -1.21 to -0.35). We found equivocal evidence for the effect of education on self-efficacy, but no significant benefit on medication adherence or on reducing interference with daily activities. Patient-based educational interventions can result in modest but significant benefits in the management of cancer pain, and are probably underused alongside more traditional analgesic approaches.
-
Although many patients with multiple sclerosis (MS) complain of trigeminal neuralgia (TN), its cause and mechanisms are still debatable. In a multicentre controlled study, we collected 130 patients with MS: 50 patients with TN, 30 patients with trigeminal sensory disturbances other than TN (ongoing pain, dysaesthesia, or hypoesthesia), and 50 control patients. All patients underwent pain assessment, trigeminal reflex testing, and dedicated MRI scans. ⋯ We conclude that the most likely cause of MS-related TN is a pontine plaque damaging the primary afferents. Nevertheless, in some patients a neurovascular contact may act as a concurring mechanism. The other sensory disturbances, including ongoing pain and dysaesthesia, may arise from damage to the second-order neurons in the spinal trigeminal complex.
-
Comparative Study
Deficiency in endogenous modulation of prolonged heat pain in patients with Irritable Bowel Syndrome and Temporomandibular Disorder.
Females with Irritable Bowel Syndrome (IBS) and Temporomandibular Disorder (TMD) are characterized by enhanced sensitivity to experimental pain. One possible explanation for this observation is deficiencies in pain modulation systems such as Diffuse Noxious Inhibitory Control (DNIC). In a few studies that used brief stimuli, chronic pain patients demonstrate reduced DNIC. ⋯ Compared to controls, IBS and TMD patients reported an increased sensitivity to heat pain and failed to demonstrate pain inhibition due to DNIC. Controls showed a significant reduction in pain during the DNIC session. These findings support the idea that chronic pain patients are not only more pain sensitive but also demonstrate reduced pain inhibition by pain, possibly because of dysfunction of endogenous pain inhibition systems.
-
Complex regional pain syndrome, which is characterised by pain and trophic disturbances, develops frequently after peripheral limb trauma. There is an increasing evidence of an involvement of the immune system in CRPS, and recently we showed that CRPS patients have autoantibodies against nervous system structures. Therefore we tested the sera of CRPS patients, neuropathy patients and healthy volunteers for surface-binding autoantibodies to primary cultures of autonomic neurons and differentiated neuroblastoma cell lines using flow cytometry. ⋯ Our data show that about 30-40% of CRPS patients have surface-binding autoantibodies against an inducible autonomic nervous system autoantigen. These data support an autoimmune hypothesis in CRPS patients. Further studies must elucidate origin and function of these autoantibodies in CRPS.