INTERACTION BETWEEN INSULIN AND OPIOID SYSTEM IN THE FORMALIN TEST OF MICE

Effects of insulin (1, 2 and 3 IU/kg, i.p.), morphine (5mg/kg, i.p.), naloxone (5mg/kg, s.c.), insulin before morphine and after naloxone were studied in the formalin test of mice. Formalin test was induced by intraplantar injection of formalin (20m, 5%). Morphine alone and insulin with morphine decreased the first phase (0-5 min) of pain. Naloxone increased the interphase (6-20 min) of niciception. Insulin and morphine decreased the second phase (21-40 min) of pain. Insulin enhanced the morphine - induced antinociception. Naloxone attenuated the suppressive effect of insulin. It seems that the antinociceptive effect of insulin in the formalin test may be dependent on the activation of opioid system