Morphine, but not tropisetron, inhibits copper sulphate-induced emesis

Abstract

The effect of tropisetron and morphine injected intravenously upon emesis caused by oral copper sulphate was investigated in unanaesthetized cats. Morphine, but not tropisetron, inhibited the emetic response to copper sulphate. Only the inhibition of percentage of cats showing emesis was dose-dependent. The most sensitive to the inhibitory effect of morphine was number of vomits. These results suggest that morphine might be a putative central inhibitory neurotransmitter, although its peripheral effect cannot be excluded with certainty. In addition, the present experiments support the view that morphine is a broad spectrum antiemetic drug.