LHRH self priming of gonadotrophin secretion: time course of development

The luteinizing hormone-releasing hormone (LHRH) self-priming effect, in which the gonadotrophin secretory response to LHRH is augmented by prior exposure to LHRH, was studied in vitro using pituitaries of proestrous rats. Individual, quartered anterior pituitaries were superfused for 6 h at 1 ml/min. Using two or three 10-min LHRH pulses of 0.8 nM in which the interpulse interval was 20-170 min or a single 2-h LHRH pulse of 0.8 nM, LHRH self priming of luteinizing hormone (LH) secretion was demonstrable within 30-40 min of LHRH exposure. LHRH self priming of follicle-stimulating hormone occurred 40-50 min after the start of LHRH exposure. The first derivative of the 2-h LHRH pulse rate of secretion vs. time curve provided a sensitive indicator of the time required for development of the self-priming response. Once initiated by a 10-min LHRH pulse, priming of LH secretion persisted with no decrease, as determined by the area under the secretion rate vs. time curve and by the slope of the rise of this curve, over the longest interpulse interval examined, 170 min. The observed time course of development and persistence of LHRH self priming are consistent with its presumed important role in development of the preovulatory gonadotrophin surges.