Kisspeptin Neurons in the Ovine Arcuate Nucleus and Preoptic Area Are Involved in the Preovulatory Luteinizing Hormone Surge

Oct 13, 2009Endocrinology

Kisspeptin cells in sheep brain regions control the hormone surge before ovulation

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Abstract

The percentage of kisspeptin cells that were Fos immunoreactive increased after acute estradiol treatment in the caudal and mid-arcuate nucleus.

Kisspeptin is produced by the Kiss1 gene and is important for regulating the release of GnRH.
Kiss1 mRNA-expressing cells are located in the preoptic area and arcuate nucleus of sheep.
Expression of Kiss1 mRNA is elevated in the caudal arcuate nucleus during the late-follicular phase of the estrous cycle.
Kisspeptin neurons in the caudal arcuate nucleus may play a role in the positive feedback mechanism that triggers the preovulatory GnRH/LH surge.
No differences in kisspeptin/Fos colocalization were observed in the preoptic area across treatment groups.

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Kisspeptin is the product of the Kiss1 gene that regulates GnRH secretion. In sheep, Kiss1 mRNA-expressing cells are found in the preoptic area (POA) and arcuate nucleus (ARC), and expression is up-regulated in the caudal ARC during the periovulatory period. We hypothesized that kisspeptin neurons in the ARC are activated by estradiol-17beta prior to the preovulatory LH surge. Ovariectomized ewes were treated as follows: 1) estradiol-17beta implants (sc 2 wk) to cause tonic negative feedback; 2) vehicle (no estrogen negative or positive feedback); or 3) positive feedback/GnRH surge-inducing injection of estradiol-17beta (50 microg iv). For groups 2 and 3, brains were collected 1 h after treatment and kisspeptin/Fos immunoreactivity was examined. In the caudal and mid-ARC, the percentage of kisspeptin cells that were Fos immunoreactive increased after acute estradiol treatment (group 3) over that seen in the other two groups. Kisspeptin/Fos colocalization was also quantified in ewes during the luteal and late-follicular phase of the estrous cycle, showing a trend toward an increase in colocalization in the late-follicular phase. Kisspeptin/Fos colocalization was similar in the POA across groups in both experiments. Analysis of Kiss1 mRNA by in situ hybridization revealed an increase in expression during the late-follicular phase in the caudal ARC and POA. These data suggest kisspeptin neurons located in the caudal extent of the ARC are involved in generating the positive feedback preovulatory GnRH/LH surge in the ewe, but there may also be a role for Kiss1-expressing cells in the POA.

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Kisspeptin Neurons in the Ovine Arcuate Nucleus and Preoptic Area Are Involved in the Preovulatory Luteinizing Hormone Surge

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