‘Ultrashort’ Feedback Control of Follicle-Stimulating Hormone-Releasing Factor Secretion

Subcutaneous administration of crude rat hypothalamic extracts containing FSH-RF and devoid of any FSH and sex steroid contamination gives rise to a considerable reduction of FSH- RF stores in the hypothalamus of castrated-hypophysectomized rats. It is suggested that the brain contains receptors sensitive to circulating levels of FSH-RF and, possibly, of other releasing factors; it is also postulated that FSH-RF might directly regulate its own production, through what might be called an ‘ultrashort’ feedback effect.