Effect of peripherally administered kisspeptin-10 on GnRH neurosecretion into the hypophyseal portal circulation in ovariectomized goat does

Kisspeptin has been shown to potently stimulate LH secretion in various species. The purpose of the present study was to determine whether the stimulatory effect of kisspeptin on LH secretion is mediated by GnRH neurosecretion into the hypophyseal portal circulation of goats. Three ovariectomized Shiba goats were implanted with an apparatus for the collection of portal blood from the pituitary portal vessels. After 7-10 days of recovery, portal and peripheral blood samples were collected for 6 h at 6-min intervals, and 500 μg (0.38 μmol)/goat of human kisspeptin-10 (kp-10), the C-terminal amidated 10-amino-acid sequence of kisspeptin, was administered via an intravenous catheter at 2 h of blood sampling. In all three goats, circulating GnRH concentrations in the portal plasma increased immediately after kp-10 administration. The increase was temporally associated with an increase in LH concentration in the peripheral circulation. The percent change in the AUC (area under the curve) of GnRH concentrations, relative to total AUC of GnRH, during the 30-min period after the kp-10 administration was significantly higher, compared to that during the pre-administration period (32.8 ± 24.4% vs 4.8 ± 1.6%). The present study demonstrates that the peripheral administration of kp-10 stimulates GnRH neurosecretion into the hypophyseal portal circulation, and thus strongly suggests that kisspeptin's action on LH secretion is mediated by GnRH.