Submitted to: Journal of Neuroendrocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2011
Publication Date: 8/15/2011
Publication URL: http://handle.nal.usda.gov/10113/59680
Citation: Redmond, J.S., Baez-Sandoval, G.M., Spell, K.M., Spencer, T.E., Lents, C.A., Williams, G.L., Amstalden, M. 2011. Developmental changes in hypothalamic Kiss1 expression during activation of the pulsatile release of luteinising hormone in maturing ewe lambs. Journal of Neuroendrocrinology. 23(9):815-822. Interpretive Summary: Failure of replacement females to become pregnant is a major source of economic loss for the livestock industry. The hypothalamus, located within the brain, controls the onset of reproductive cycles by regulating the release of reproductive hormones from the pituitary gland. However, the mechanisms that govern this process are not clearly identified. Kisspeptin is a hormone that is speculated to play an important role in this event. To test this, researchers from Texas A&M University, in collaboration with ARS scientists, correlated expression of the kisspeptin gene in the hypothalamus with concentrations of luteinizing hormone in ewe lambs. They discovered that expression of the gene for kisspeptin was increased in the hypothalamus near the time of the onset of puberty, and that the amount of kisspeptin gene expressed was associated with the rate of secretion of luteinizing hormone from the pituitary gland. This indicates that kisspeptin is involved in the initiation of reproductive cycles in sheep. This research forms the basis for future studies to determine how this occurs, and is an important step toward the long-term goal of maximizing fertility in replacement females.
Technical Abstract: Onset of puberty is characterized by a marked increase in the frequency of release of gonadotrophin-releasing hormone (GnRH) and luteinizing hormone (LH). The KISS1 gene plays a critical role in pubertal development and its product, kisspeptin, stimulates GnRH and LH release. In the study reported herein, we tested the hypothesis that KISS1 gene expression in the preoptic area (POA) and hypothalamus increases during maturation of the reproductive neuroendocrine axis in association with increased LH pulsatility. Ovariectomized, oestradiol-replaced lambs were euthanized at 25, 30 and 35 wk of age. Blood samples were collected before euthanasia to characterize the pattern of LH release. KISS1 mRNA was detected in coronal sections of the POA and hypothalamus and KISS1-expressing cells were identified on the basis of silver grain density. The mean number of KISS1-expressing cells in the POA/periventricular (PeV) areas increased from 25 to 30 wk of age. No further increase at 35 wk of age was observed, and the changes in KISS1 expression in the POA/PeV were independent of LH pulse frequency. In the arcuate nucleus (ARC), the mean number of KISS1–expressing cells did not differ among age groups per se, but was greater in lambs exhibiting increased frequency of LH release. Density of silver grains per cell did not differ among groups in any of the areas studied. Results indicate that kisspeptin neurons in the ARC are involved in the acceleration of pulsatile LH release during maturation of the reproductive neuroendocrine axis in ewe lambs.