Complete Blockade and Attenuation of 5–Hydroxytryptamine Induced Analgesia Following NA Depletion in Rats and Mice

Abstract

The effect of pretreatment with the noradrenaline neurotoxin, N–2–chloroethyl–N–ethyl–2–bromobenzylamine (DSP4), upon the analgesia induced by various doses of 5–hydroxytryptamine (5–HT) was examined in rats and mice. DSP4 treatment (2 × 50 mg/kg, intraperitoneally) of rats caused a complete blockade of 5–HT induced analgesia in the tail–flick, hot–plate and shock titration tests. DSP4 treatment (1 × 50 mg/kg, intraperitoneally) of mice caused a partial blockade of 5–HT induced analgesia in the hot–plate test, but no significant blockade in the tail–flick test. These results are discussed with regard to serotonergicnoradrenergic interactions and the species discrepancy in nociceptive testing