Direct Anterior Pituitary Modulation of Gonadotropin Secretion by Neuropeptide Y: Role of Gonadal Steroids

Abstract

Neuropeptide Y (NPY) acts at the hypothalamus to stimulate LH secretion through increased LHRH secretion. NPY is also cosecreted into the portal system in a pulsatile manner with LHRH and may act at the anterior pituitary to increase LH secretion through potentiation of LHRH responsiveness and possibly through direct stimulation; however, controversy exists concerning this direct action of NPY at the pituitary. Utilizing dispersed anterior pituitary monolayer cell cultures, the first goal of this study was to determine the effects of vehicle, 10(-10) M LHRH, 10(-7) M NPY, 10(-6) M NPY, 10(-10) M LHRH + 10(-7) M NPY, and 10(-10) M LHRH + 10(-6) M NPY on LH and FSH responsiveness. Under these conditions, 10(-6) M NPY alone significantly stimulated LH secretion (630% above basal) and both 10(-7) M NPY and 10(-6) M NPY significantly potentiated LHRH-induced LH secretion (195 and 244% above LHRH alone, respectively). Neither 10(-7) M NPY nor 10(-6) M NPY alone stimulated FSH secretion; however, both 10(-7) M and 10(-6) M NPY significantly potentiated LHRH-induced FSH secretion (130 and 135% above LHRH alone, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)