Synchronization of the Ovarian Cycle of the Ewe After Surgical Suppression of the Corpus Luteum

Lang, D. R.

doi:10.1530/jrf.0.0090113

Cited by 10 publications

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…304), the ewe returned to oestrus 2 days later. This finding is in agreement with those of McKenzie & Terrill (1937), Lang (1965) and Robert¬ son (1969). The progesterone levels in the plasma confirmed that ovulation did occur, and a functional corpus luteum developed (Text-fig.…”

Section: Resultssupporting

confidence: 93%

Studies on the Growth and Atresia of Graafian Follicles in the Ovary of the Sheep

Smeaton¹,

Robertson²

1971

Reproduction

112

View full text Add to dashboard Cite

The growth and atresia of individual Graafian follicles in the ovaries of fourteen cycling Suffolk ewes were followed in vivo by marking the large follicle(s) present in the ovaries with Indian ink at three different times during the oestrous cycle. The ovaries containing marked follicles were removed on the 3rd to 9th day of the next cycle and sectioned to determine whether the follicles had ovulated. The results showed that follicles marked before the last day of the cycle regressed and did not ovulate. Only large follicles marked at, or just before, the onset of oestrus, ovulated and developed into corpora lutea. It is suggested that there are at least three phases of follicular growth and atresia during any one oestrous cycle which appear to be independent of circulating progesterone levels. Examination of sections of ovaries from a number of anoestrous and pregnant ewes gave no indication of a similar cyclic pattern of follicular growth and atresia.

show abstract

Section: Resultssupporting

confidence: 93%

Studies on the Growth and Atresia of Graafian Follicles in the Ovary of the Sheep

Smeaton¹,

Robertson²

1971

Reproduction

112

View full text Add to dashboard Cite

show abstract

“…Thus, ovulation cannot occur during the luteal phase of the oestrous cycle when endogenous progesterone levels are raised (3,4). Further, the LH surge in the ewe can be blocked by artificially maintaining elevated circulating levels of this ovarian steroid, or the timing advanced by removal of the corpus luteum, the major ovarian source of progesterone (5). The neural mechanisms underlying progesterone negative feedback are poorly understood.…”

mentioning

confidence: 99%

Inhibition of Luteinizing Hormone Secretion in the Ewe by Progesterone: Associated Changes in the Release of Gamma‐Aminobutyric Acid and Noradrenaline in the Preoptic Area as Measured by Intracranial Microdialysis

Robinson

Kendrick

1992

J Neuroendocrinology

View full text Add to dashboard Cite

Progesterone inhibits the pulsatile release of luteinizing hormone (LH) in sheep by an action in the brain to suppress the release of LH-releasing hormone (LHRH). In addition, progesterone blocks the preovulatory surge of LH in this species. The neural basis of this inhibitory action is unknown, but as LHRH cells do not appear to contain progestin receptors other neural systems must mediate the action of this ovarian steroid on LH release. This study focuses on a possible role for the inhibitory amino-acid GABA and the monoamines (noradrenaline, adrenaline, dopamine and serotonin). The technique of microdialysis was used to monitor changes in these substances in the vicinity of the LHRH cell bodies (in the preoptic area) both before and following the administration of progesterone. Levels of this steroid, similar to those measured during the mid-luteal phase of the oestrous cycle, inhibited LH release and this was associated with significant alterations in the release of GABA and noradrenaline (but not adrenaline, dopamine or serotonin). Specifically, progesterone augmented GABA while noradrenaline release was depressed. Whether steroid actions on these neurotransmitters were mediated by opioids was also investigated. This possibility arises because of the reported involvement of opioids in progesterone negative feedback in the ewe. The long-acting opioid antagonist, naltrexone, was administered and GABA and noradrenaline release monitored for a further period both in the presence and absence of progesterone. Naltrexone significantly depressed GABA release in steroid-treated (but not untreated) ewes suggesting that the actions of progesterone on GABA are mediated by the endogenous opioid peptides. However, noradrenaline release was unaltered. In an earlier study we demonstrated that GABA release fell prior to the LH surge while noradrenaline release increased. These data, in conjunction with those from the present study, suggest that the mechanism by which progesterone is able to inhibit the preovulatory surge of LH in the ewe is by enhancing GABA and depressing noradrenaline release in the vicinity of the LHRH cell bodies. As opioid tone is also reported to fall prior to the surge, the interaction between opiate and GABAergic systems in the regulation of gonadotrophin secretion warrants further investigation.

show abstract

“…-39 -Παρόμοια, η αφαίρεση του ωχρού σωματίου στην προβατίνα, έχει σαν αποτέλεσμα η ωοθυλακιορρηξία να λάβει χώρα μετά από χρονικό διάστημα ίσο με την ωοθυλακική φάση (Lang, 1965-Robertson, 1969Smeaton και Robertson, 1971-Dufour et al, 1971. Αυτό σημαίνει ότι, η απουσία του ωχρού σωματίου στην προβατίνα θα είχε σαν αποτέλεσμα ο οιστρικός κύκλος να διαρκεί 4 μέρες (Robertson, 1969).…”

Section: 9unclassified

Τροποποιηση Του Ανοσοποιητικου Συστηματος Της Αιγας Για Αυξηση Του Ρυθμου Αναπαραγωγης

Αυδη¹

View full text Add to dashboard Cite

Την κ. Κ. ΚΟΝΣΟΥΛΤΟΥ, για τη δακτυλογράφηση και επιμέλεια των κειμένων στον Η/Υ, την υπομονή της και τις ελεύθερες ώρες που κατανάλωσε, ευχαριστώ ιδιαίτερα. Τον ζωοκόμο κ. Ι. ΝΤίΛΛΗ, για τη βοήθεια στην εκτέλεση του πειραματισμού.Τέλος, θα ήθελα να ευχαριστήσω θερμά τη συνάδελφο και φίλη κ. Π. ΠΑΝΑΓΙΩΤΑΚΗ, για τη υλική και ηθική βοήθεια που μου προσέφερε.

show abstract

Synchronization of the Ovarian Cycle of the Ewe After Surgical Suppression of the Corpus Luteum

Cited by 10 publications

References 2 publications

Studies on the Growth and Atresia of Graafian Follicles in the Ovary of the Sheep

Studies on the Growth and Atresia of Graafian Follicles in the Ovary of the Sheep

Inhibition of Luteinizing Hormone Secretion in the Ewe by Progesterone: Associated Changes in the Release of Gamma‐Aminobutyric Acid and Noradrenaline in the Preoptic Area as Measured by Intracranial Microdialysis

Τροποποιηση Του Ανοσοποιητικου Συστηματος Της Αιγας Για Αυξηση Του Ρυθμου Αναπαραγωγης

Contact Info

Product

Resources

About