Articles: hyperalgesia.
-
Review
The Underestimated Significance of Conditioning in Placebo Hypoalgesia and Nocebo Hyperalgesia.
Placebo and nocebo effects are intriguing phenomena in pain perception with important implications for clinical research and practice because they can alleviate or increase pain. According to current theoretical accounts, these effects can be shaped by verbal suggestions, social observational learning, and classical conditioning and are necessarily mediated by explicit expectation. In this review, we focus on the contribution of conditioning in the induction of placebo hypoalgesia and nocebo hyperalgesia and present accumulating evidence that conditioning independent from explicit expectation can cause these effects. ⋯ Because only few studies have investigated clinical samples, the picture seems less clear when it comes to patient populations with chronic pain. However, conditioning appears to be a promising means to optimize treatment. In order to get a better insight into the mechanisms of placebo and nocebo effects in pain and the possible benefits of conditioning compared to explicit expectation, future studies should carefully distinguish both methods of induction.
-
It has been suggested that repeated overload might sensitize nociceptors, causing local hyperalgesia in patients with patellofemoral pain (PFP). This might also lead to generalized hyperalgesia, indicative of altered central pain processing. This study aimed to investigate differences in pressure pain threshold (PPT) as a measure of pressure hyperalgesia between patients with PFP and healthy controls and in predefined subgroups and to study associations between PPT and patient characteristics. ⋯ Local and generalized pressure hyperalgesia, suggesting alterations in both peripheral and central pain processing, were present in patients with PFP, though females with PFP were most likely to suffer from generalized hyperalgesia.
-
Objective Although nociceptive sensitisation is an important pathophysiological process in migraine and migraine chronification, its underlying mechanisms remain unclear. Toll-like receptor 4 (TLR4), a pattern-recognition molecule, has a critical role in both neuropathic pain and morphine tolerance. The present study examined whether elements of the TLR4 pathway contribute to hyperalgesia induced by dural inflammation in rats. ⋯ The inflammatory soup stimulus increased the production of TLR4 downstream molecules and interleukin-1 beta. Higher levels of microglia activation and brain-derived neurotrophic factor release were observed following the administration of the inflammatory soup but were alleviated by TAK-242. Conclusions These data suggest that the TLR4 signalling pathway promotes hyperalgesia induced by acute inflammatory soup delivery by stimulating the production of proinflammatory cytokines and activating microglia.
-
Background Lithium is widely used to treat bipolar disorders and displays mood stabilizing properties. In addition, lithium relieves painful cluster headaches and has a strong analgesic effect in neuropathic pain rat models. Objectives To investigate the analgesic effect of lithium on the cuff model of neuropathic pain. ⋯ Biochemical analyses highlight a significant increase in beta-endorphin levels by 30% in the brain of lithium-treated mice compared to controls. No variation of beta-endorphin was detected in the blood. Conclusions Together, our results provide evidence that lithium induces a long-lasting analgesia in neuropathic mice presumably through elevated brain levels of beta-endorphin and the activation of MORs.
-
Various spinal cord stimulation (SCS) modes are used in the treatment of chronic neuropathic pain disorders. Conventional (Con) and Burst-SCS are hypothesized to exert analgesic effects through different stimulation-induced mechanisms. Preclinical electrophysiological findings suggest that stimulation intensity is correlated with the effectiveness of Burst-SCS. Therefore, we aimed to investigate the relation between amplitude (charge per second) and behavioral effects in a rat model of chronic neuropathic pain, for both Conventional Spinal Cord Stimulation (Con-SCS) and biphasic Burst-SCS. ⋯ Biphasic Burst-SCS requires significantly more mean charge per second in order to achieve similar pain relief, as compared with Con-SCS, in an experimental model of chronic neuropathic pain.