Articles: hyperalgesia.
-
An electrophysiologic study to examine responses of dorsal horn neurons in the rat L5 spinal cord to noxious stimuli after disc herniation or application of the nucleus pulposus to the L5 nerve root. ⋯ Results suggest that somewhat pathogenic factors in the nucleus pulposus may have a crucial role in the induction of hyperalgesia. This may help to elucidate the reason why a severe pain is sometimes induced without a visually identified protrusion.
-
Neutral endopeptidase (EC3.4.24.11, NEP, enkephalinase) is a zinc-metalloendopeptidase, cleaving a variety of substrates like enkephalins, substance P, and bradykinin. In the brain, NEP is a key enzyme in the degradation of enkephalins. Pharmacological inhibition of NEP-activity causes analgesia resulting from enhanced extracellular enkephalin concentrations. ⋯ Similarly, the nitric oxide synthase inhibitor L-NAME reduced writhing in NEP-knockouts. These results indicate that genetic elimination of NEP, in contrast to pharmacological inhibition, leads to bradykinin-induced hyperalgesia instead of enkephalin-mediated analgesia. Nitric oxide (NO) is suggested to be involved in this process.
-
Tissue damage may produce hyperalgesia, allodynia, and persistent pain. The authors recently reported that fentanyl elicits analgesia but also activates N-methyl-D-aspartate-dependent pain facilitatory processes opposing analgesia. In nonsuffering rats, this leads to a long-lasting enhancement in pain sensitivity. The current study assessed whether fentanyl could amplify carrageenan-induced hyperalgesia. ⋯ Central sensitization in inflammatory pain states is reinforced by an opiate treatment, which could be prevented by N-methyl-D-aspartate receptors blockade.
-
Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used as analgesics. Although the results of clinical studies indicate considerable disparity in the analgesic efficacy of NSAIDs, the pre-clinical models generally used for the study of nociception do not allow a clear distinction to be made between the analgesic properties of agents belonging to this family. As clinical pain is characterized by hyperalgesia, we evaluated the effects of NSAIDs with similar chemical structures but different selectivities for cyclo-oxygenase (COX)-1 and COX-2 in a new behavioural model of central hyperalgesia in rats. ⋯ However, only lornoxicam was fully effective for prevention of hyperalgesia. Our results indicate a dissociation between the anti-inflammatory and the anti-hyperalgesic activity of NSAIDs, where the latter seems to be more evident after the block of both COX-1 and COX-2. Finally, they suggest that our experimental model of thermal hindpaw hyperalgesia can be effectively utilized to assess the ability of different drugs to reduce central sensitization, and thus hyperalgesia.
-
Neuroscience letters · Jan 2002
Capsaicin sensitive afferents mediate the development of heat hyperalgesia and hindpaw edema after sciatic section in rats.
Sciatic section in rats evokes chronic hyperalgesia, autotomy pain behavior, and hindpaw edema, a constellation resembling complex regional pain syndrome (CRPS) in man. Glucocorticoid treatment inhibits these sequelae of sciatic section and also blocks neurogenic extravasation. ⋯ Now, we show that pre-emptive destruction of the small diameter fibers prevents neurogenic extravasation, and prevented the development of heat hyperalgesia and hindpaw edema after sciatic section. Thus, capsaicin sensitive primary afferent neurons which release SP are required for the development of heat hyperalgesia and hindpaw edema in this animal model of CRPS.