The role of serotonin as a mediator of emesis induced by different stimuli.

Abstract

The aim of this work was to evaluate the impact of changes in serotonin metabolism on the pathophysiology of different types of emesis: pregnancy-induced emesis, emesis associated with inner-ear dysfunction, and cisplatin-induced emesis. The urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), the main metabolite of serotonin, was measured in 13 women with pregnancy-induced emesis, 12 patients who had nausea and vomiting following inner-ear dysfunctions, 27 patients with cisplatin-induced emesis and a control group of 21 women. 5-HIAA was measured with a fluorescence polarization immunoassay (Abbott) and corrected for varying urine concentrations. Both patients with emesis associated with inner-ear dysfunction and patients with pregnancy-associated emesis showed a similar 5-HIAA excretion pattern compared with the control group. No correlation between intensity of nausea or vomiting and changes in 5-HIAA excretion could be detected. In patients receiving cisplatin, the 5-HIAA excretion increased rapidly within the 12 h following cisplatin administration and returned to baseline levels after 24 h. There was a parallel increase of 5-HIAA excretion and numbers of emetic episodes in the first 12 h, but delayed emesis was not associated with elevated 5-HIAA excretion. Our results provide evidence that serotonin is involved in the pathophysiology of cisplatin-induced acute emesis. Cisplatin-induced delayed emesis, pregnancy-associated emesis, and emesis due to inner-ear dysfunction are not associated with elevated levels of 5-HIAA excretion. The serotonin pathway probably represents only one of many different afferent mechanisms capable of initiating the emesis cascade.