Cholecystokinin stimulation leads to increased oxytocin secretion in women

Objective: To find out if cholecystokinin (CCK) stimulates the secretion of oxytocin in humans. and if there are any differences in secretion between healthy women and those with normal-transit constipation. Design: Prospective open study. Setting: Teaching hospital, Sweden. Subjects: 8 healthy female volunteers and 6 women with chronic refractory normal-transit constipation. Interventions: Subjects were fasted before experiments. On one day they were given emulsified corn oil and another an intravenous injection of 1 Ivy dog unit (IDU) CCK/kg body weight. Blood samples were taken before each experiment at 10 minutes and at the time the experiments started. Blood samples were also taken after each experiment at 10, 20, 30, 45, 60, 90 and 120 minutes. Main outcome measures: Concentrations of CCK and oxytocin. Results: Ingestion of corn oil significantly increased the plasma concentration of CCK in both groups (healthy women p=0.03 and constipated women p=0.008). Injection of CCK also led as expected to hypercholecystokininaemia in both groups (p=0.008 and p=0.03. respectively). The corn oil increased oxytocin secretion in both groups (p=0.02 and 0.03, respectively) and exogenous CCK increased the secretion still further (p=0.008 and 0.03, respectively). Conclusions: Both corn oil and injection of CCK led to an increased CCK concentration in plasma. Oxytocin was secreted in response to endogenous as well as exogenous CCK stimulation. There was no difference between healthy and constipated women in either parameter analysed.