ANTINOCICEPTION INDUCED BY SM-32 DEPENDS ON A 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 mu g per mouse i.c.v.) and abdomi nal constriction (10-30 mg kg(-1) i.p) tests. In the antinociceptive d ose-range, SM 32 did not impair mouse spontaneous motility and motor c oordination evaluated respectively by the Animex and rota-rod tests. T he increase in the pain threshold produced by SM 32 was prevented by d icyclomine, pirenzepine and hemicholinium-3 but not by naloxone and CG P 35348. In vitro experiments showed that the SM 32 amplified electric ally- and nicotine-evoked guinea-pig ileum contractions, On the basis of the above data, it can be postulated that SM 32 exerts its antinoci ceptive effect through a potentiation of central cholinergic transmiss ion. (C) 1997 The Italian Pharmacological Society.