Seasonal Variation in the Gonadotropin-Releasing Hormone Response to Kisspeptin in Sheep: Possible Kisspeptin Regulation of the Kisspeptin Receptor

Abstract

Kisspeptin signaling in the hypothalamus appears critical for the onset of puberty and driving the reproductive axis. In sheep, reproduction is seasonal, being activated by short days and inhibited by long days. During the non-breeding (anestrous) season, gonadotropin-releasing hormone (GnRH) and gonadotropin secretion is reduced, as is the expression of Kiss1 mRNA in the brain. Conversely, the luteinizing hormone response to kisspeptin during this time is greater. To determine whether the GnRH response to kisspeptin is increased during anestrus, we utilized hypophysial portal blood sampling. In anestrus ewes, the GnRH and LH responses to kisspeptin were greater compared to the breeding seas..