The aim of the present study was to investigate the hormone, sexual behaviour and neuropeptide profiles of follicular phase ewes and examine alterations after the application of acute stressors. In study 1, follicular phases of intact ewes were synchronised with progesterone vaginal pessaries. Ewes then received saline vehicle, insulin (4 iu/kg) or endotoxin (LPS; 100ng/kg) at 28h after progesterone withdrawal (PW; time zero). In study 2, this protocol was repeated, but animals were killed at 0h, 16h, 31h and 40h after PW and brain tissue retrieved. In study 1, there was a delay of 17.6h and 7.2h (P<0.05), respectively, in half the insulin-treated animals (‘insulin-delayed’) but not in the other half; and a delay of 22.5h and 20.7h (P<0.001), respectively, in all LPS-treated animals. Plasma oestradiol concentrations decreased after both stressors (P<0.001) and cortisol increased in all groups (P<0.05); whereas progesterone increased in the insulin-delayed and LPS groups only (P<0.05). In study 2, immunohistochemistry was used to examine transcriptional activation (co-expression with c-Fos) of various neuropeptides in the hypothalamus and preoptic area. In control ewes, the maximum percentage of dynorphin cells co-localising c-Fos (i.e., activated) was observed at 31h after PW (52%; P<0.05), whereas maximum activated kisspeptin and neurokinin B cells occurred at 40h after PW (49 and 42%, respectively; P<0.05). The percentage of activated dopamine cells decreased before the onset of sexual behaviour (from 70 to 26%; P<0.05) whereas β-endorphin activation was lower during the LH surge (from 41 to 10%; P<0.05). In contrast, neuropeptide Y and somatostatin activation was higher during the surge (from 21 to 36%; P<0.08; and from 14 and 9% to 47 and 73%, respectively; P<0.05). However, LPS decreased the percentage of activated dynorphin cells (to 11%; P<0.05) and kisspeptin cells (to 22%; P<0.05). On the contrary, insulin decreased the percentage of activated dynorphin cells (to 27%) in two of the insulin-treated animals (insulin-responders) but not in the other two; whereas the percentage of activated kisspeptin cells increased in all insulin-treated animals (52%; P<0.05). Neurokinin B was not altered by either treatment. Furthermore, insulin increased the percentage of activated β-endorphin, neuropeptide Y and somatostatin cells in the ARC (to 71, 72 and 63%, respectively, P<0.05) but LPS did not have the same effect. In the VMN, activation of somatostatin cells was greater in all LPS treated animals (from 8 to 27%; P<0.05) but only in two of the insulin-treated animals (to 55 and 76%; insulin-responders) but not in the other two (to 5 and 6%; insulin-non-responders). These results indicate that there is a specific hormonal, behavioural and neuropeptide pattern during the follicular phase of intact ewes and this is disturbed by acute LPS or insulin administration in the late follicular phase, leading to the disruption of the LH surge.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:559393 |
| Date | January 2011 |
| Creators | Fergani, Chrysanthi |
| Contributors | Dobson, Hilary. ; Smith, Rob. ; Pickavance, Lucy |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/4173/ |
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