Pain
-
The anti-nociceptive and locomotor effects of the nicotinic acetylcholine receptor (nAChR) agonists (+)-epibatidine and ABT-594 were compared in the rat. Acute thermal nociception was measured using the tail flick test. Mechanical hyperalgesia was measured as paw withdrawal threshold (PWT) in response to a mechanical stimulus in two animal models of persistent pain; (1) 24 h following subplantar injections of Freund's complete adjuvant (FCA) into the left hind paw or (2) 11-15 days following a partial ligation of the left sciatic nerve. ⋯ In summary, ABT-594 is less potent than (+)-epibatidine in assays of acute and persistent pain and in the rotarod assay. However, ABT-594 displayed a clearer separation between its motor and anti-hyperalgesic effects. This shows that nicotinic agonists with improved selectivity between the nicotinic receptor subtypes could provide strong analgesic effects with a much improved therapeutic window.
-
Randomized Controlled Trial Clinical Trial
Ketamine reduces muscle pain, temporal summation, and referred pain in fibromyalgia patients.
Central mechanisms related to referred muscle pain and temporal summation of muscular nociceptive activity are facilitated in fibromyalgia syndrome (FMS) patients. The present study assessed the effects of an NMDA-antagonist (ketamine) on these central mechanisms. FMS patients received either i.v. placebo or ketamine (0.3 mg/kg, Ketalar((R))50% decrease in pain intensity at rest by active drug on two consecutive VAS assessments). ⋯ The present study showed that mechanisms involved in referred pain, temporal summation, muscular hyperalgesia, and muscle pain at rest were attenuated by the NMDA-antagonist in FMS patients. It suggested a link between central hyperexcitability and the mechanisms for facilitated referred pain and temporal summation in a sub-group of the fibromyalgia syndrome patients. Whether this is specific for FMS patients or a general phenomena in painful musculoskeletal disorders is not known.
-
In an attempt to explain how and why some individuals with musculoskeletal pain develop a chronic pain syndrome, Lethem et al. (Lethem J, Slade PD, Troup JDG, Bentley G. Outline of fear-avoidance model of exaggerated pain perceptions. Behav Res Ther 1983; 21: 401-408).ntroduced a so-called 'fear-avoidance' model. ⋯ We also review the available assessment methods for the quantification of pain-related fear and avoidance. Finally, we discuss the implications of the recent findings for the prevention and treatment of chronic musculoskeletal pain. Although there are still a number of unresolved issues which merit future research attention, pain-related fear and avoidance appear to be an essential feature of the development of a chronic problem for a substantial number of patients with musculoskeletal pain.
-
Clinical Trial
Some empirical evidence regarding the validity of the Spanish version of the McGill Pain Questionnaire (MPQ-SV).
Despite the fact that the McGill Pain Questionnaire (MPQ) is a useful pain assessment tool with widespread acceptance, empirical analyses have questioned its validity because they have not consistently supported the three a priori factors that guided its construction. The Spanish version that has followed the most systematic and rigorous reconstruction process (Lázaro C, Bosch F, Torrubia R, Banos JE. The development of a Spanish Questionnaire for assessing pain: preliminary data concerning reliability and validity. ⋯ In relation to concurrent evidence, significant correlations (0.001) were found between each subscale and the criteria measurements of every pain dimension. Only the affective subscale presented discriminant validity. Evidence supports the validity of the affective and sensory subscales but not the evaluative scale.
-
The anterior cingulate cortex (ACC) and adjacent regions in the medial wall have been implicated in sensory, motor and cognitive processes, including pain. Our previous functional magnetic resonance imaging (fMRI) studies have demonstrated pain-related activation of the posterior portion of the ACC during transcutaneous electrical nerve stimulation (TENS) and variable patterns of cortical activation with innocuous and noxious thermal stimuli in individual subjects. The present study represents the companion paper to our recent study of pain- and thermal-related cortical activations with the aim to use fMRI to delineate the activations in the ACC and surrounding regions of the medial wall during application of innocuous and noxious thermal stimuli as well as during performance of a motor task in individual subjects. ⋯ Although the present results demonstrate intersubject variability in the task-related activations, some general modality-specific patterns were apparent: (i) innocuous thermal-related activations were located mainly in the anterior ACC; (ii) noxious thermal-related activations were primarily located in the anterior ACC, the ventral portion of the posterior ACC, and the supplementary motor area (SMA); (iii) motor-related activations were primarily located in the SMA and dorsal portion of the posterior ACC. These results indicate that specific spatial patterns of activation exist within the ACC and surrounding regions of the medial wall for innocuous and noxious thermal stimuli, and that noxious thermal- and motor-related activations appear to be segregated within the ACC. Therefore, we propose a segregation of the ACC into an anterior non-specific attention/arousal system and a posterior pain system.