Articles: pain-threshold.
-
To calibrate or not to calibrate? This question is raised by almost everyone designing an experimental pain study with supra-threshold stimulation. The dilemma is whether to individualize stimulus intensity to the pain threshold / supra-threshold pain level of each participant or whether to provide the noxious stimulus at a fixed intensity so that everyone receives the identical input. Each approach has unique pros and cons which need to be considered to i) accurately design an experiment, ii) enhance statistical inference in the given data and, iii) reduce bias and the influence of confounding factors in the individual study e.g., body composition, differences in energy absorption and previous experience. ⋯ PERSPECTIVE: To calibrate pain or not? This dilemma is related to almost every experimental pain research. The decision is a trade-off between statistical power and greater control of stimulus encoding. The article decomposes both approaches and presents the pros and cons of either approach supported by data and simulation experiment.
-
Kv4 channels are key components controlling neuronal excitability at membrane potentials below action potential thresholds. It remains elusive whether Kv4.1 participates in pain regulation. ⋯ Based on the expression of Kv4.1 and Kv4.3 in the nociceptors, Kv4.1 in the secondary nociceptive neurons, Kv4.1 in spinal lamina I excitatory interneurons that regulate the activity of the secondary nociceptive neurons, as well as Kv4.2 and Kv4.3 in spinal lamina II excitatory interneurons that also regulate the activity of the secondary nociceptive neurons, developing Kv4 activators or genetic manipulation to increase Kv4 channel activity in these pain-related Kv4+ neurons will be useful in future pain therapeutics.
-
Autonomic nervous system dysfunction has been implicated in chronic whiplash-associated disorder (WAD). However, the relationship between autonomic variables (e.g., resting heart rate and blood pressure) and clinical factors in chronic WAD is not well understood. This study sought to examine the associations between resting heart rate, resting blood pressure, pain processing and psychological variables in chronic WAD and in pain-free controls. ⋯ An association between blood pressure and pain sensitivity was observed in the control group but not the chronic WAD group. Such an association appears to be disrupted in chronic WAD, which may infer involvement of autonomic pathways in the pathophysiology of this condition.
-
Transient receptor potential vanilloid-1 (TRPV1), activated by heat, acidic pH, endogenous vanilloids and capsaicin, is essential for thermal hyperalgesia. Under inflammatory conditions, phosphorylation of TRPV1 by protein kinase C (PKC) can sensitize the channel and decrease the activation threshold. Src kinase also phosphorylates TRPV1, promoting channel trafficking to the plasma membrane. These post-translational modifications are important for several chronic pain conditions. This study presents a previously undescribed relationship between Src and PKC phosphorylation of TRPV1, influencing the thermal hypersensitivity associated with TRPV1 activation. ⋯ Src kinase-mediated phosphorylation of TRPV1 is a critical regulator of the PKC-induced sensitization induced by multiple inflammatory mediators. This suggest a new regulatory mechanism governing TRPV1 function and a potential therapeutic target for inflammatory type pain, including cancer pain where Src antagonists are currently utilized.
-
Meta Analysis
Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes.
Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. ⋯ Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm ( P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area ( P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.