Antinociceptive action of picrotoxin in the mouse.

Picrotoxin, an antagonist of GABA-associated chloride ionophores with convulsant activity, possesses antinociceptive activity in the hot-plate and writhing tests in the mouse. Analgesia produced by a subconvulsant dose of picrotoxin (0.75 mg/kg, s.c.) was reversed by naloxone (1.0 mg/kg, s.c.), atropine (5 mg/kg, i.p.), and methysergide (10 mg/kg, i.p.) in the jumping reaction (hot-plate test). These data indicate that opiate pathways, as well as cholinergic and serotoninergic pathways could be involved in the mechanism that underlies picrotoxin-induced analgesia. Furthermore, such results should be considered when interpreting the behavioral effects of picrotoxin.