Plasma Concentration of Prolactin during Four-day Osmotic Pump Infusion of Thyrotropin-Releasing Hormone and Vasoactive Intestinal Polypeptide in Rats

Abstract

Pituitary prolactin (PRL) responses to 4-day continuous infusion of thyrotropin- releasing hormone (TRH) and vasoactive intestinal polypeptide (VIP) were investigated in unanesthetized male rats using Alzet osmotic minipumps. The TRH dose infused was 3.6μg/day and the VIP dose was 32.8μg/day. Infusion of TRH with osmotic pumps elevated the plasma PRL level compared to controls over the 4-day infusion period. However, mean levels of PRL tended to decrease during the 4-day infusion. On the other hand, continuous VIP infusion elicited a significant continuous PRL release over the 4-day infusion period. Thus, it may be said that the PRL responses to infused TRH and VIP were maintained during the 4-day infusion.