An automated method by which effects of compounds on locomotor activity and spontaneous neuropathic pain-specific movements can be simultaneously evaluated in rats with chronic-constriction nerve injury

Impairment in locomotor activity as an objective measure of pain and analgesia in a rat model of osteoarthritis

A major problem with current animal models of pain is their lack of face validity and their vulnerability for false positive results. The present study evaluated the efficacy of the open field locomotor system, as an objective measure of pain-related behavior and analgesic efficacy in rodents. Adult, male, Sprague-Dawley rats (180-250 g) received intra-articular injections of monoiodoacetate (MIA; 1 mg) in the left knee joint. Mechanical allodynia using von Frey filaments, the weight bearing difference test and the open field locomotor activity test were performed every other day for 21 days, following the MIA injection. The antinociceptive effects of ibuprofen (50 and 100 mg/kg) on the MIA-induced nociception were also evaluated. MIA induced a significant reduction in the paw withdrawal threshold (PWT) and a significant alteration in the weight bearing difference compared with control rats. Similarly, MIA induced a significant reduction in locomotor activity, with respect to X total counts, that represent the overall locomotor activity in the horizontal plane, and X ambulatory counts, which in turn represent small scale movements, such as scratching and grooming, and lastly, Z total counts, that represent rearing or standing. Both doses of ibuprofen resulted in a significant reversal of the MIA-induced alterations in PWT and weight bearing difference. Furthermore, the two doses of ibuprofen resulted in a significant reversal of the MIA-induced reduction in locomotor activity, with respect to X ambulatory counts, but not Z total counts. Only the higher dose of ibuprofen reversed the X total counts. The open field locomotor system may successfully be used to predict the analgesic efficacy of compounds in models of joint inflammation and osteoarthritis.

The role of P2X4 receptors in chronic pain: A potential pharmacological target

Chronic pain is a common symptom of most clinical diseases, which seriously affects the psychosomatic health of patients and brings some pain to patients. Due to its pathological mechanism is very complicated and the treatment of chronic pain has always been a difficult problem in clinical. Normally, drugs are usually used to relieve pain, but the analgesic effect is not good, especially for cancer pain patients, the analgesic effect is poor. Therefore, exploring the pathogenesis and treatment of chronic pain has aroused the interest of many researchers. A large number of studies have shown that the role of ATP and P2X4 receptor (P2X4R) play an important role in the pathogenesis of chronic pain. P2X4R is dependent on ATP ligand-gated ion channel receptor, which can be activated by ATP and plays an important role in the information transmission of nerve system and the formation of pain. Therefore, in this paper, we comprehensively described the structure and biological functions of P2X4R, and outlined behavioral evaluation methods of chronic pain models. Moreover, we also explored the inherent relationship between P2X4R and chronic pain, and described the therapeutic effect of P2X4R antagonist on chronic pain, and provided some valuable help for the treatment of chronic pain.