effect of blood glucose level changes on the formalin - induced pain in mice

the effect of blood glucose level changes induced by 24h food deprivation and intraperitoneal (ip) injection of insulin (2iu/kg) and glucose (2gr/kg) was investigated on the pain induced by intraplantar (ipl) injection of formalin (20ml , 5%) in mice. blood glucose level changes were determined by blood sampling from the apex of the tail of mice. ip injection of insulin and 24h food deprivation decreased and ip injection of glucose increased the blood glucose level. ipl injection of formalin produced a marked biphasic pain response with a quiescent phase between them. insulin and food deprivation reduced the late (inflammatory) phase of pain. exogenous glucose increased the quiescent phase of formalin pain. it seems that hypoglycemia and hyperglycemia may not have a role in neurogenic pain. hypoglycemia reduces the inflammatory pain. hyperglycemia produces hyperalgesia by increasing the pain response in the quiescent phase.