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Kisspeptin signaling is required for the luteinizing hormone response in anestrous ewes following the introduction of males.

De Bond JA, Li Q, Millar RP, Clarke IJ, Smith JT - PLoS ONE (2013)

Bottom Line: Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male.Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry.We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Monash University, Melbourne, Victoria, Australia.

ABSTRACT
The introduction of a novel male stimulates the hypothalamic-pituitary-gonadal axis of female sheep during seasonal anestrus, leading to the resumption of follicle maturation and ovulation. How this pheromone cue activates pulsatile secretion of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) is unknown. We hypothesised that pheromones activate kisspeptin neurons, the product of which is critical for the stimulation of GnRH neurons and fertility. During the non-breeding season, female sheep were exposed to novel males and blood samples collected for analysis of plasma LH profiles. Females without exposure to males served as controls. In addition, one hour before male exposure, a kisspeptin antagonist (P-271) or vehicle was infused into the lateral ventricle and continued for the entire period of male exposure. Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male. Infusion of P-271 abolished this effect of male exposure. Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry. In addition, the per-cell expression of Kiss1 mRNA was increased in the rostral and mid (but not the caudal) arcuate nucleus (ARC) after male exposure in both aCSF and P-271 treated ewes, but the per-cell content of neurokinin B mRNA was decreased. There was also a generalized increase in Fos positive cells in the rostral and mid ARC as well as the ventromedial hypothalamus of females exposed to males. We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion.

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Male exposure in anestrous ewes resulted in Fos induction in GnRH neurons.A, Bright-field photomicrographs indicate GnRH (brown) and Fos (black) neurons (arrows) in the mPOA. Single labled GnRH neurons are indicated by open triangles. Scale bar, 100 µm. B–C, The percentage of GnRH neurons co-expressing Fos and the number of GnRH/Fos neurons was greater in male exposed ewes compared to ewes not exposed to males (Control – aCSF). Kisspeptin antagonist treatment (P-271) reduced the percentage and number of GnRH cells co-expressing Fos in male exposed ewes. Data are the mean ± SEM, ***P<0.001, **P<0.01, n = 4 per group.
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pone-0057972-g004: Male exposure in anestrous ewes resulted in Fos induction in GnRH neurons.A, Bright-field photomicrographs indicate GnRH (brown) and Fos (black) neurons (arrows) in the mPOA. Single labled GnRH neurons are indicated by open triangles. Scale bar, 100 µm. B–C, The percentage of GnRH neurons co-expressing Fos and the number of GnRH/Fos neurons was greater in male exposed ewes compared to ewes not exposed to males (Control – aCSF). Kisspeptin antagonist treatment (P-271) reduced the percentage and number of GnRH cells co-expressing Fos in male exposed ewes. Data are the mean ± SEM, ***P<0.001, **P<0.01, n = 4 per group.

Mentions: Although there was no overall change in Fos labeling in the mPOA, there was a trend for an increase following male exposure. To test whether a sub-population of these Fos-ir cells were GnRH neurons, we examined the co-expression of GnRH and Fos in the mPOA (Figure 4). Male exposure in anestrous ewes resulted in a 5-fold increase in the percentage of mPOA GnRH cells co-labeling for Fos compared with controls (P<0.001, Figure 4). Infusion of P-271 did not prevent GnRH neuron activation following male exposure, but the percentage was significantly less (P<0.01) than that seen in male exposed, aCSF treated ewes. The number of GnRH/Fos neurons mirrored that of percentage expressing FOS (Figure 4 C).


Kisspeptin signaling is required for the luteinizing hormone response in anestrous ewes following the introduction of males.

De Bond JA, Li Q, Millar RP, Clarke IJ, Smith JT - PLoS ONE (2013)

Male exposure in anestrous ewes resulted in Fos induction in GnRH neurons.A, Bright-field photomicrographs indicate GnRH (brown) and Fos (black) neurons (arrows) in the mPOA. Single labled GnRH neurons are indicated by open triangles. Scale bar, 100 µm. B–C, The percentage of GnRH neurons co-expressing Fos and the number of GnRH/Fos neurons was greater in male exposed ewes compared to ewes not exposed to males (Control – aCSF). Kisspeptin antagonist treatment (P-271) reduced the percentage and number of GnRH cells co-expressing Fos in male exposed ewes. Data are the mean ± SEM, ***P<0.001, **P<0.01, n = 4 per group.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585258&req=5

pone-0057972-g004: Male exposure in anestrous ewes resulted in Fos induction in GnRH neurons.A, Bright-field photomicrographs indicate GnRH (brown) and Fos (black) neurons (arrows) in the mPOA. Single labled GnRH neurons are indicated by open triangles. Scale bar, 100 µm. B–C, The percentage of GnRH neurons co-expressing Fos and the number of GnRH/Fos neurons was greater in male exposed ewes compared to ewes not exposed to males (Control – aCSF). Kisspeptin antagonist treatment (P-271) reduced the percentage and number of GnRH cells co-expressing Fos in male exposed ewes. Data are the mean ± SEM, ***P<0.001, **P<0.01, n = 4 per group.
Mentions: Although there was no overall change in Fos labeling in the mPOA, there was a trend for an increase following male exposure. To test whether a sub-population of these Fos-ir cells were GnRH neurons, we examined the co-expression of GnRH and Fos in the mPOA (Figure 4). Male exposure in anestrous ewes resulted in a 5-fold increase in the percentage of mPOA GnRH cells co-labeling for Fos compared with controls (P<0.001, Figure 4). Infusion of P-271 did not prevent GnRH neuron activation following male exposure, but the percentage was significantly less (P<0.01) than that seen in male exposed, aCSF treated ewes. The number of GnRH/Fos neurons mirrored that of percentage expressing FOS (Figure 4 C).

Bottom Line: Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male.Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry.We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Monash University, Melbourne, Victoria, Australia.

ABSTRACT
The introduction of a novel male stimulates the hypothalamic-pituitary-gonadal axis of female sheep during seasonal anestrus, leading to the resumption of follicle maturation and ovulation. How this pheromone cue activates pulsatile secretion of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) is unknown. We hypothesised that pheromones activate kisspeptin neurons, the product of which is critical for the stimulation of GnRH neurons and fertility. During the non-breeding season, female sheep were exposed to novel males and blood samples collected for analysis of plasma LH profiles. Females without exposure to males served as controls. In addition, one hour before male exposure, a kisspeptin antagonist (P-271) or vehicle was infused into the lateral ventricle and continued for the entire period of male exposure. Introduction of a male led to elevated mean LH levels, due to increased LH pulse amplitude and pulse frequency in females, when compared to females not exposed to a male. Infusion of P-271 abolished this effect of male exposure. Brains were collected after the male effect stimulus and we observed an increase in the percentage of kisspeptin neurons co-expressing Fos, by immunohistochemistry. In addition, the per-cell expression of Kiss1 mRNA was increased in the rostral and mid (but not the caudal) arcuate nucleus (ARC) after male exposure in both aCSF and P-271 treated ewes, but the per-cell content of neurokinin B mRNA was decreased. There was also a generalized increase in Fos positive cells in the rostral and mid ARC as well as the ventromedial hypothalamus of females exposed to males. We conclude that introduction of male sheep to seasonally anestrous female sheep activates kisspeptin neurons and other cells in the hypothalamus, leading to increased GnRH/LH secretion.

Show MeSH
Related in: MedlinePlus