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.