ANTINOCICEPTIVE EFFECT OF ALPHA-TRINOSITOL, A NOVEL D-MYO-INOSITOL PHOSPHATE DERIVATIVE, IN THE FORMALIN TEST IN RATS

The antinociceptive effect of alpha-trinositol was examined in rats us ing the formalin test following systemic, spinal and local subcutaneou s administration. Injection of formalin into the paw evoked two phases (phase 1: 0-9 min; phase 2: 10-60 min) of flinching behavior of the i njected paw. Intrathecal administration of alpha-trinositol resulted i n a dose-dependent suppression of the first (ED(50): 8 mu g) and secon d (ED(50): 9 mu g) phase of formalin-evoked behavioral response. Simil arly, intraperitoneal delivery showed a dose-dependent reduction of th e first (ED(50): 83 mg/kg) and second (ED(50): 56 mg/kg) phase of the formalin test. Subcutaneous injection of 100 mu g, but not 10 mu g, al pha-trinositol into the rat paw together with the formalin solution, h ad no effect on the first phase, but reduced by 20% the second phase o f behavior. These data show that alpha-trinositol produces a suppressi on of acute and prolonged nociceptive behaviors with a central mechani sm of action, although some peripheral component may contribute to the reduction of the late phase following systemic administration.