Oxytocin enhances the prolactin response to vasoactive intestinal polypeptide in healthy women

Abstract

Objective: To establish whether oxytocin modifies the stimulatory effect of vasoactive intestinal polypeptide (VIP) on prolactin secretion in healthy women. Design: Controlled clinical study. Setting: Healthy women in an academic research environment. Patient(s): Seven healthy women (aged 24–32 years) were tested on the 22nd day of two consecutive normal menstrual cycles. Intervention(s): Vasoactive intestinal polypeptide (4 pmol · kg −1 · min −1 in 50 mL of normal saline infused IV for 60 minutes) was administered in either the presence or absence of concurrent treatment with oxytocin (2 IU injected plus 0.07 IU/min infused for 60 minutes). Main Outcome Measure(s): Serum prolactin levels. Result(s): The administration of VIP induced a significant increase in serum prolactin levels, with a mean peak response 1.6 times higher than baseline at 45 minutes after injection. In the presence of oxytocin, the prolactin response to VIP was significantly higher, with a mean peak response 2 times higher than baseline. Conclusion(s): These data suggest that in healthy women, oxytocin facilitates the regulation of the stimulating effect of VIP on prolactin secretion.