Endocrine Abstracts

Evidence from studies in goats¹, sheep² and mice³ suggests that the kisspeptin cells of the arcuate nucleus generate the signal that causes the pulsatile secretion of GnRH. This effect may be due to action of kisspeptin on GnRH terminals in the median eminence^3,4. We conducted studies on sheep to test the hypothesis that kisspeptin cells of the arcuate nucleus (ARC) and/or the glutamate cells of the hypothalamus pulses of GnRH secretion.

Blood samples were taken each 10 min for 3 h from 18 ewes in the luteal phase of the estrous cycle. The animals were euthanased and the brains perfused with 4% paraformaldehyde. LH assays showed that 3 animals had a pulse of luteinising hormone (LH) within 30 min of brain collection. In these (pulse) and 3 other animals (non-pulse) we determined the number of GnRH, kisspeptin and glutamate cells in the hypothalamus that co-stained for c-Fos. Sections were cut through the ARC and the preoptic area (POA) and the peptides were visualised in cells by immunohistochemistry. The sections were then co-stained for c-Fos as an indicator of neuronal activation. Pulse generation was associated with a significant (P<0.002) increase in the mean (±S.E.M.) percentage of ARC kisspeptin cells with c-Fos staining (pulse −74.9±2.5% vs no pulse −, 34.4±6.1%). In the ARC, more (P<0.01) glutamate cells were c-Fos labelled (27.6±4.4) in pulse animals than in non-pulse animals (5.8±0.6). There was no difference in the number of kisspeptin, glutamate or GnRH cells co-staining for c-Fos in the POA.

These data suggest that kisspeptin cells of the ARC generate GnRH pulses, but glutamate cells may also be involved.

References: Ohkura et al. (2009) J Neuroendocrinol. 21 813.

Merkley et al. (2012) Endocrinol. 2012 153(11) 5406.

D’Anglemont Tassigny et al. (2008) Endocrinol. 149 3926

Smith et al. (2011) Endocrinology. 152 1001.