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In non-breeding ewes the kisspeptin analog C6 triggers ovulation without progestogen priming

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In non-breeding ewes the kisspeptin analog C6 triggers ovulation without progestogen priming

In non-breeding ewes the kisspeptin analog C6 triggers ovulation without progestogen priming

Toronto (July 2018)

Introduction :

Kisspeptin system is central to regulate the reproductive axis activity. We have demonstrated that a single injection of C6, a kisspeptin-10 analog, when combined with a progestogen treatment triggers fertile ovulations in the ewe in the breeding and non-breeding season. In present work we tested if in the non-breeding season C6 would be able to induce ovulation without progestogen priming. This information would extend our knowledge on the physiological action of the kisspeptin system and would also be useful for possible field application of kisspeptin analogs.

Materials and Methods :

Intact ile de France ewes were injected intramuscularly during the non-breeding season either with a single dose of C6 (1, 5, 15, 45 nmol/ewe). Intact of OVX+E (feedback negative dose) were also injected two or three times at 36 or 48-hour intervals with 15 nmol/ewe of C6.  Serial blood samples were collected from the jugular vein at short time inertval to measure LH and FSH by RIA, and than daily up to 10 days post-injection to assess progesteron level by ELISA

Results :

Effect of single im injection of increasing doses of C6 on plasmatic hormonal profile

Profils Hormonaux après injection du C6 en intra musculaire

Même à la dose la plus faible (1 nmol / brebis), le C6 a augmenté les concentrations plasmatiques de LH et de FSH. Cependant, seule la dose de 15 nmol / brebis a déclenché une certaine ovulation. Dans un cas avec une phase lutéale normale de 14 jours (diamant violet) et l'autre avec un cycle plus court (triangle vert). Toutes les autres doses étaient inactives.

Shéma Effet de l'injection répétée de C6

Only the first C6 injection elicited a significant increase of LH plasma concentration. GnRH injection at the end of the 12-hour interval regimen induced a minor LH increase. (Arrows indicate injection time)
Shéma Effets injection répétée C6 sur brebis intactes

Also in intact ewes only the first injection elicited a significant LH increase. However, both treatments triggered ovulation with the 48 hour-interval regimen apparently beeing more effective.

Conclusions :

Regardless to the dose a single C6 injection is ineffective in triggering ovulation during the non-breeding season. Conversely, three injections at 36- or 48-hours interval consistently triggers ovulation. However, only the first injection elicited an LH increase, the lack of effect of subsequent injections is probably E-independent because present also in OVX+E. These results suggesting the existence of other sites of action for C6, warrant further investigation

Modification date : 02 August 2023 | Publication date : 07 August 2018 | Redactor : VR