5 years ago

The two populations of kisspeptin neurons are involved in the ram induced LH pulsatile secretion and LH surge in anestrous ewes.

Exposure to a ram during spring stimulates luteinizing hormone (LH) secretion and can induce ovulation in sexually quiescent ewes ("ram effect"). Kisspeptins (Kiss) present in the arcuate nucleus (ARC) and the preoptic area (POA) are potent stimulators of LH secretion. Our aim was to investigate if Kiss neurons mediate the increase in LH secretion during the "ram effect". With double immunofluorescent detection we identified Kiss neurons (Kiss IR) activated (Fos IR) by exposure to a ram for 2h (M2), 12h (M12) or to ewes for 2h (C). The density of cells Kiss + Fos IR and the proportion of Kiss IR also Fos IR cells was higher in M2 and M12 than in C in ARC (p<0.002) and POA (p<0.02). In ARC these parameters were also higher in M12 than in M2 (p<0.02 and p<0.05). Kiss antagonist (P234 10-6M) administered by retrodialysis in POA for 3 h at the time of introduction of the ram greatly reduced the amplitude of the male-induced increase in LH concentration compared to solvent (p<0.02). In ARC, P234 had more limited effect (p<0.038 1h after P234) but pulse frequency increased less than after solvent (p=0.07). In contrast Kiss antagonist (P271 10-4M) infused in ARC but not POA 6 to 18 h after introduction of the ram prevented the LH surge in the ewe (0/6 versus 4/5 and 4/6 in C). These results suggest that both populations of Kiss neurons are involved in the ram induced pulsatile LH secretion and in the LH surge.

Publisher URL: http://doi.org/10.1210/en.2017-00429

DOI: 10.1210/en.2017-00429

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