ANTINOCICEPTION INDUCED BY SM32 DEPENDS ON CENTRAL CHOLINERGIC MECHANISM

The antinociceptive effect of SM 32 was examined in mice by using the hot-plate (10–40 mg kg-1 i.p; 3–30 mg per mouse i.c.v.) and abdominal constriction (10–30 mg kg-1 i.p) tests. In the antinociceptive dose-range, SM 32 did not impair mouse spontaneous motility and motor coordination evaluated respectively by the Animex and rota-rod tests. The increase in the pain threshold produced by SM 32 was prevented by dicyclomine, pirenzepine and hemicholinium-3 but not by naloxone and CGP 35348. In vitro experiments showed that the SM 32 amplified electrically- and nicotine-evoked guinea-pig ileum contractions. On the basis of the above data, it can be postulated that SM 32 exerts its antinociceptive effect through a potentiation of central cholinergic transmission.