Further Evidence that Luteinizing Hormone-Releasing Hormone also Is Follicle-Stimulating Hormone-Releasing Hormone

While LHRH evokes the release of both LH and FSH under a wide spectrum of experimental conditions, this hormone has not been shown to induce the discharge of FSH unaccompanied by LH release. As a consequence, the possibility that a separate FSHRH exists has not been discounted. These experiments were designed to demonstrate that LHRH is capable of promoting marked increases in plasma FSH concomitant with physiologically insignificant changes in plasma LH and, thus, that LHRH is also FSHRH. Seven groups of cyclic female rats received phenobarbital at 1200 h proestrus to block spontaneous preovulatory LH and FSH surges. These various groups then were subdivided according to whether phosphate-buffered saline (PBS), LHRH, or both was infused (iv). The experimental protocol consisted of infusing material for an initial 30 min (priming period), stopping the infusion for 30 min (rest interval), and again infusing material for an additional 210 min (maintenance period). When PBS was infused during the priming and...