Kisspeptin immunoreactive cells of the ovine preoptic area and arcuate nucleus co-express estrogen receptor alpha.

Kisspeptins are peptide ligands of the G protein-coupled receptor GPR54, recently shown to be essential to reproductive function. We have raised specific rabbit antisera against a highly conserved 10 amino acid-amidated peptide (kp10) common to all kisspeptin isoforms isolated so far and mapped the distribution of kp10-immunoreactive (ir) cells in the ovine hypothalamus. Kp10-ir cells were predominant in the caudal arcuate nucleus, the dorsomedial nucleus and the medial preoptic area. Numerous varicose kp10-ir fibers were found in the preoptic area where GnRH neurons reside and in the median eminence, seemingly projecting around small capillaries in its external zone. Within the caudal arcuate nucleus, nearly all kp10-ir cells showed an intense estradiol receptor alpha immunofluorescent signal compared with approximately half of kp10-ir cells in the preoptic area. The pattern of distribution of kp10 immunoreactivity in the hypothalamus suggests a role for kisspeptin in the estrogen-dependent regulation of GnRH and LH secretion in the ewe.