A multi-target ligand (JM-20) prevents morphine-induced hyperalgesia in naïve and neuropathic rats

Abstract

The present study examines the possible inhibitory effect of JM-20, a multi-target neuroprotective compound, on the development of morphine-induced hyperalgesia in Male Sprague-Dawley naïve rats. Additionally, the impact of JM-20 on chronic constriction injury (CCI) rats under chronic morphine exposure was investigated, and its efficacy in reducing mechanical hypersensitivity and histopathological changes in the sciatic nerve was assessed. JM-20 (20 mg/kg, per os [p.o.]), administered 60 min before morphine (10 mg/kg, s.c. twice daily at 12 h intervals) for ten days, significantly inhibited the development of morphine-induced hyperalgesia assessed using an electronic pressure-meter paw test, hot-plate, and formalin test, as well as the appearance of spontaneous withdrawal somatic symptoms in rats. Furthermore, JM-20 decreases spinal pro-inflammatory interleukin-1β and restores glutathione to close physiological concentrations, biomarkers directly related to the intensity of mechanical hypernociception. After CCI and sham surgery, co-treatment with JM-20 (10 mg/kg, p.o.) for five days decreased morphine increased-mechanical hypersensitivity, even 12 days after its discontinuation. Continued morphine treatment imposed a neuroinflammatory challenge in CCI animals, further increasing cellularity (>75% immune cell infiltration) with lymphocytes and macrophages. However, JM-20 co-treatment still reduced the presence of cellular infiltrates (51–75%) with a predominance of lymphocytes. Even in the absence of nerve injury, JM-20 attenuated the peripheral neuroinflammatory response observed in morphine-treated sham-operated animals (0% vs. 1–25%). These findings suggest that JM-20 could prevent morphine-induced hyperalgesia by anti-inflammatory and antioxidant mechanisms.