Estrogen alters the effects of neuropeptide-Y on luteinizing hormone and follicle-stimulating hormone release in female rats at the level of the anterior pituitary gland.

Abstract

In recent years, several studies have shown that neuropeptide-Y (NPY) is involved in the control of LH secretion. We determined the effects of estrogen on NPY-induced LH and FSH release in the absence or presence of LH-releasing hormone (LHRH) at the level of the anterior pituitary gland (APG). Adult female rats were ovariectomized. Fifteen to 20 days later, they were given a blank or estrogen-filled capsule subdermally and killed 17-19 h later. APG cells were isolated and cultured for 3 days in medium containing 12.5% rat serum collected at death from the same rats used to make the respective APG cell pools. The cells were then challenged for 3 h with vehicle, NPY (10(-12)-10(-6) M), LHRH (10(-9)-10(-6) M), or combinations of NPY (10(-9)-10(-7) M) and LHRH (10(-9) M). LHRH stimulated LH and FSH release from nonestrogen and estrogen-primed cells. NPY at 6.7 x 10(-8)-10(-6) M increased (P < 0.05) LH release and at 10(-6) M increased (P < 0.05) FSH release from estrogen-primed cells, but was without effect on nonestrogen-primed cells. In contrast, NPY at 10(-9)-10(-7) M potentiated the action of LHRH (10(-9) M) to increase the release of LH and FSH from nonestrogen-primed cells, but was without potentiating effects in cultures of estrogen-primed cells. The results demonstrate that 1) NPY can release LH and FSH by a direct action on estrogen-primed APG cells; and 2) NPY can potentiate the action of LHRH to increase the release of LH and FSH by a direct action on nonestrogen-primed APG cells.

Orexin A Interactions in the Hypothalamo-Pituitary Gonadal Axis

“…Similarly, NPY has been shown to have effects on LH release in vitro that are dependent on gonadal steroid milieu (23,24). The opposite effects of orexin A on the HPG at the pituitary and hypothalamus are not unusual and have been reported for other peptides (25).…”

Neuroanatomical Framework of the Metabolic Control of Reproduction

“…The suppression of basal LH levels by fasting fails in NPY knockout mice (208). However, pharmacological studies in rodents and primates (106,494) have suggested that the NPY has a dual action on the HPG axis according to sex steroids milieu. NPY has suppressive effects on LH pulse amplitude and frequency when sex steroids are low and a robust activational effect following steroid replacement in gonadectomized rats (38,106,301).…”