Summary

Recently, evidence has accumulated that supports a role of spinal microglia in chronic pain, especially the facilitation of neuropathic pain. Astrocytes activate neuronal sensitization not only through inflammatory cytokines, but also more directly by release of glutamate, suggesting this target for new pain therapies. Therefore, in this study we tried to examine the astroglia in the spinal cord of streptozotocin-induced diabetic rats and the ability of NMDA-receptor blockers to suppress allodynia and hyperalgesia in them. Diabetes was induced in adult male Wistar rats by a single i.p. injection of streptozotocin (70 mg/kg; plasma glucose concentrations>15 mmol/l). The acute analgesic effects of ketamine (5, 10 and 30 mg/kg, i.p.), MK-801 (0.1 mg/kg, i.p.) were examined. Paw pressure and von Frey tests were used to measure nociceptive thresholds. Light and electron microscopy were applied to reveal the glia in spinal cord. Ketamine was effective against mechanical allodynia. Thermal and mechanical hyperalgesia were reversed in dose-dependent manner. MK-801 possessed a pronounced activity against mechanical allodynia. Astrocytes were found to be more numerous than in controls both electron microscopically and by immunofluorescent histochemistry. Possibly astroglia is involved in the neuropathic pain and NMDA-receptor blockers alleviated it in streptozotocin-induced diabetic rats. Key words: streptozotocin-induced diabetes, spinal cord, glial cells, NMDA-receptor blockers, rat