Apomorphine-induced nausea in humans: release of vasopressin and pancreatic polypeptide.

Based on studies in animals and humans, it has been suggested that nausea activates the hypothalamo-neurohypophyseal system with resultant increases in circulating concentrations of oxytocin or vasopressin. The purpose of these studies was to determine in humans whether nausea is associated with increases in circulating concentrations of neurohypophyseal hormones or various enteropancreatic peptides (vasoactive intestinal polypeptide, substance P, or pancreatic polypeptide). Nausea, induced by intravenous infusion of apomorphine, was associated with fivefold to 75-fold increases in plasma vasopressin concentrations in 7 subjects (mean increase, 41-fold), with no change in plasma oxytocin levels. Furthermore, nausea was associated with sevenfold to 16-fold increases in plasma pancreatic polypeptide concentrations (mean increase, ninefold), with no change in plasma levels of vasoactive intestinal polypeptide or substance P. In 1 subject refractory to nausea, there was no increase in plasma vasopressin or pancreatic polypeptide concentrations with apomorphine. These studies indicate that nausea in humans is associated with vasopressin and pancreatic polypeptide release.