A study of the hypothalamic pulse-generating mechanism responsible for LH release: electrical stimulation of the medial basal hypothalamus in the ovariectomized guinea pig.

In order to examine the neurophysiological properties of the hypothalamus responsible for the pulsatile release of luteinizing hormone (LH) the medial basal hypothalamus (MBH) of the ovariectomized adult female guinea pig was stimulated electrically through an implanted electrode and LH release was monitored as an indication of luteinizing hormone-releasing hormone (LHRH) release. Electrical stimulation (ES) consisting of monophasic square wave pulses with 0.5 ms pulse duration was applied for 2 min at 60, 40, 20, or 10 min intervals. Current intensity (80, 200, 500 microA) and frequency (8, 50, 100 Hz) were varied to determine the parameters of ES which resulted in an LH pulse with amplitude similar to that of a pulse induced by the endogenous pulse-generating mechanism. Blood samples were collected at 5 or 10 min intervals through an indwelling catheter, and LH was measured by RIA.(ABSTRACT TRUNCATED AT 250 WORDS)