Vasopressin release in response to nausea-producing agents and cholecystokinin in monkeys

Administration of lithium chloride and copper sulfate to adult monkeys caused marked elevations in plasma vasopressin (AVP) levels without significant increases in plasma oxytocin (OT) levels. Emesis was produced in five of the seven animals given these agents, in support of nausea as the main stimulus to AVP release. A similar pattern of AVP release without OT release was found after administration of cholecystokinin (CCK). Although most monkeys vomited in response to 10 micrograms/kg of CCK, a significant increase in plasma AVP levels also was produced with a dose of 1 microgram/kg, which did not produce emesis in any animal. These findings are in marked contrast with previous results in rats, which indicated that lithium chloride, copper sulfate, and CCK each stimulated OT rather than AVP release. Despite this interspecies difference, the significant neurohypophysial hormone secretion in response to both nausea-producing agents and CCK suggests that AVP secretion in monkeys, similar to OT secretion in rats, might reflect activation of central pathways mediating nausea and/or inhibition of food intake, even when overt illness is not produced.