THE ANALGESIC EFFECT OF CLONIXINE IS NOT MEDIATED BY 5-HT3 SUBTYPE RECEPTORS

1. The analgesic effect of clonixinate of L-lysine (Clx) in the nocice ptive C-fiber reflex in rat and in the writhing test in mice is report ed. 2. Clx was administered by three routes, i.v., i.t. and i.c.v., in ducing a dose-dependent antinociception. 3. The antinociceptive effect of Clx was 40-45% with respect to the control integration values in t he nociceptive C-fiber reflex method. 4. The writhing test yielded ED5 0 values (mg/kg) of 12.0 +/- 1.3 (i.p.), 1.8 +/- 0.2 (i.t.) and 0.9 +/ - 0.1 (i.c.v.) for Clx administration. 5. Ondansetron was not able to antagonize the antinociception response of Clx in the algesiometric te sts used. 6. Chlorophenilbiguanide did not produce any significative c hange in the analgesic effect of Clx in the nociceptive C-fiber reflex method. 7. It is suggested that the mechanism of action of the centra l analgesia of Clx is not mediated by 5-HT3 subtype receptors.