Pulsatile GnRH administration stimulates the number of pituitary GnRH receptors in seasonally anoestrous ewes

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Authors:
M. Khalid
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,
W. Haresign
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, and
M. G. Hunter
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DOI:
https://doi.org/10.1530/jrf.0.0790223
Volume/Issue:
Volume 79: Issue 1
Page Range:
223–230
Article Type:
Research Article
Online Publication Date:
Jan 1987
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Summary. Twenty seasonally anoestrous ewes were pretreated with progesterone for 4 days and divided into four equal groups. Ewes in Group 1 received no GnRH treatment and were slaughtered immediately after progesterone removal. Ewes in Groups 2, 3 and 4 received i.v. injections of 250 ng GnRH every 2 h for 36 h starting at the time of progesterone removal. Ewes in Group 2 were slaughtered immediately after the 36 h GnRH pulsing, while ewes in Groups 3 and 4 were given a bolus injection of 125 μg GnRH at this time and were slaughtered 2 and 10 h after the bolus injection, respectively. Blood samples were collected every 30 min from ewes in Group 4 only, from 4 h before the start of GnRH treatment until 10 h after the bolus injection. Pulsing with GnRH resulted in episodic release of LH, and the bolus injection of GnRH was immediately followed by a preovulatory type LH surge in those ewes in which an endogenous surge had not already begun. The pituitary GnRH receptor numbers were significantly higher for the ewes in Group 2 than for any of the other treatment groups, while there was no significant difference in the receptor numbers between Groups 1, 3 and 4. The results suggest an up-regulation of GnRH receptors resulting from pulsatile GnRH therapy.

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Print ISSN:
1470-1626
Online ISSN:
1741-7899