EFFECT OF ERGOCRISTINE ON PROLACTIN SECRETION IN THE MALE-RAT WITH PITUITARIES GRAFTED BENEATH THE KIDNEY CAPSULE

Male rats in which three pituitaries were grafted beneath the kidney capsule showed approximately a fourfold increase in circulating plasma prolactin concentration. The elevated plasma prolactin concentration did not remain at a constant level but fluctuated with time. The elevated prolactin concentration declined immediately after a single bolus injection of ergocristine (30 μg/kg). The slope of the prolactin decay curve, determined by sequential blood sampling, was parallel to a theoretical slope having a 7-min half-life. This result indicates that ergocristine blocked prolactin secretion immediately and completely as the decay curve (T 1/2 =6.5 min, confidence interval 4.5-11.3) resulting from the administration of ergocristine is the same as the endogenous prolactin decay curve (T 1/2 =7 min).