Minocycline potentiates the anti-hyperalgesic effect of ceftriaxone in CCI-induced neuropathic pain in rats

Glutamate neurotoxicity and pro-inflammatory cytokines have an important role in the central sensitization of neuropathic pain. The purpose of the present study was to evaluate anti-hyperalgesic effect of repeated administration of ceftriaxone, which selectively activates and increases the expression of glutamate transporter, as well as minocycline, a selective inhibitor of microglia activation, either alone or together in Wistar rats subjected to the chronic constriction injury (CCI) of sciatic nerve. Ceftriaxone (100, 150 and 200 mg/kg) and minocycline (25, 50 and 100 mg/kg) were administered intraperitoneally from the day of surgery for seven consecutive days. Thermal hyperalgesia was assessed by focal radiant heat source on the hind paw of animals one day before surgery and on 3, 5, 7, 10 and 14 days following that. Ceftriaxone dose dependently, attenuated thermal hyperalgesia in animals. None of the administered doses of minocycline affected the CCI induced-thermal hyperalgesia in neuropathic animals. A fixed dose of minocycline (50 mg/kg) combined with three different doses of ceftriaxone administered for 7 consecutive days yielded a potentiating effect in the enhancing latency time to noxious thermal stimulus remaining until the 14th day post-surgery. The results suggest that modulation of microglia activity could have a supportive role in the improvement of CCI-induced thermal hyperalgesia and combination of such classes of drugs which have no antibiotic effects could be a new and promising therapeutic strategy for treatment.