Inhibition of gonadotrophin release in mares during the luteal phase of the oestrous cycle by endogenous opioids

Behrens, C; Aurich, Jörg; Klug, E; Naumann, Heidrun; Hoppen, H. O.

doi:10.1530/jrf.0.0980509

Cited by 55 publications

(48 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is in contrast to cyclic mares, in which opioids inhibit LH release during the luteal phase (Behrens et al 1993). In pregnant mares less than 2 weeks later, naloxone no longer releases LH, although the oestrogenprogesterone environment is similar to that of dioestrus.…”

Section: Discussionmentioning

confidence: 74%

“…Concentrations of LH, PRL and progesterone in plasma were measured by radioimmunoassay (RIA) as described previously (Behrens et al 1993). The assay for LH utilised equine LH (Biogenesis, Poole, Dorset, UK) as the standard and for iodination, and an antibody raised in rabbits against equine LH (A 543; Biogenesis).…”

Section: Hormone Assaysmentioning

confidence: 99%

“…The intra-and interassay coefficients of variation were 4·1% and 10·3% respectively, the minimal detectable concentration was 0·25 µg/l, and the crossreactivity of the antibody with equine growth hormone (AFP 7424C, Dr A F Parlow) was <0·1% (Aurich et al 1995). Progesterone was determined by RIA after extraction from plasma with n-hexane as described previously (Behrens et al 1993). The intra-and interassay coefficients of variation were 4·5 and 7·9% respectively, and the minimal detectable concentration was 0·16 nmol/l.…”

Section: Hormone Assaysmentioning

confidence: 99%

“…In non-pregnant mares, endogenous opioids inhibit LH release during the luteal, but not the follicular, phase (Behrens et al 1993) and during the anovulatory season (Aurich et al 1994). Opioids influence LH release via the secretion of gonadotrophin-releasing hormone (GnRH) from the hypothalamus (Parvizi & Ellendorff 1980, Alexander et al 2000.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Aurich

Aurich²,

Parvizi³

2001

Journal of Endocrinology

View full text Add to dashboard Cite

In equine species, luteinising hormone (LH) and prolactin (PRL) release are reduced throughout pregnancy but increase at foaling. The present experiments were designed to study a possible opioidergic regulation of LH and PRL release in pregnant Shetland mares (n=6). At various stages of pregnancy (days 26·4 0·6, 75·4 5·4, 171·8 2·4, 226·2 4·8, 282·7 3·4 and 319·8 2·1), mares were injected with the opioid antagonist naloxone (0·5 mg/kg body weight) and saline. The two treatments were always separated by 2 days, and mares served as their own controls. Two hours after being given naloxone and saline, mares were given the gonadotrophin-releasing hormone (GnRH) analogue buserelin (5 µg per animal). The naloxone experiment was repeated at 2 days after foaling. Blood for the determination of LH and PRL was withdrawn at 15 min intervals for 240 min, and naloxone or saline was injected after 60 min. Naloxone induced significant (P<0·05) LH release on days 172, 226 and 283 of pregnancy but not on days 26, 76 and 320 and 2 days after foaling. Buserelin caused a significant (P<0·05) increase in plasma LH concentrations on days 172, 226, 282 and 320 of pregnancy. The experiments indicate that endogenous opioids are involved in the inhibition of LH release during the second half of pregnancy in equine species. The deactivation of opioid effects on LH release might be a prerequisite for the onset of ovarian activity postpartum. Plasma PRL concentrations increased significantly (P<0·05) after naloxone administration on days 226, 282 and 320 of pregnancy. The naloxone-induced PRL release was most pronounced towards term, indicating an increase in the naloxone-releasable pool and/or the absence of other PRL-release inhibitory mechanisms.

show abstract

Section: Discussionmentioning

confidence: 74%

Section: Hormone Assaysmentioning

confidence: 99%

Section: Hormone Assaysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Aurich

Aurich²,

Parvizi³

2001

Journal of Endocrinology

View full text Add to dashboard Cite

show abstract

“…They act at all levels of the hypothalamo-pituitary-gonadal axis (Blank et al 1986, Cacicedo and Sanchez-Franco 1986, Leposavic et al 1991, Smith and Gallo 1997, Kaminski et al 2004 and are also involved in gonadal steroid feedback on gonadotropin secretion from the pituitary (Barb et al 1986, Martini et al 1989, Behrens et al 1993. The action of opioids on many aspects of reproduction in mammals is mainly inhibitory (Yilmaz et al 1996, Kawamura et al 2003.…”

Section: Introductionmentioning

confidence: 99%

Interaction of ghrelin and opioids in luteinizing hormone (LH) secretion by pituitary cells of common carp, <I>Cyprinus carpio</I> (Actinopterygii: Cypriniformes: Cyprinidae), cultured in vitro

Sokolowska-Mikolajczyk¹,

Socha²,

Mikołajczyk³

et al. 2011

Acta Icth et Piscat

View full text Add to dashboard Cite

Sokołowska-Mikołajczyk M., Socha M., Mikołajczyk T., Epler P., Fałowska B. 2011. Interaction of ghrelin and opioids in luteinizing hormone (LH) secretion by pituitary cells of common carp, Cyprinus carpio (Actinopterygii: Cypriniformes: Cyprinidae), cultured in vitro. Acta Ichthyol. Piscat. 41 (2): 81-87.Background. Ghrelin, a newly discovered hormone is involved mainly in the regulation of body energy homeostasis. It has also been proved that ghrelin affects many other processes including the control of the hypothalamo-pituitary-gonadal axis in vertebrates. Ghrelin interacts also with other peptides and neurotransmitters, which are involved in gonadotropin release, such as endogenous opioid peptides. The aim of the experiment was to compare the effects of ghrelin and naltrexone, an opioid antagonist, on LH secretion by pituitary cells of mature female and male common carp, Cyprinus carpio L. Materials and methods. In the in vitro experiment the time-dependent (10 and 24 h) action of ghrelin (10 -7 or 10 -6 M) and naltrexone at 10 -6 M added alone or in combination on LH secretion by enzymatically dispersed pituitary cells of mature female and male carp (Cyprinus carpio L.) was studied.Results. Ghrelin alone at a dose of 10 -6 M stimulated LH secretion after 10 h of female-but not male-derived cell incubations. Ghrelin at 10 -7 M had no effect on LH secretion from either female or male cells. Naltrexone alone stimulated LH secretion only after 24 h of female cell culture. In male cells no significant changes in LH secretion in response to naltrexone alone were found after 10 or 24 h incubation period. Combined treatment (ghrelin 10 -7 or 10 -6 M and naltrexone) stimulated LH secretion in female and male cell incubations at 10 and 24 h: LH levels were significantly higher in comparison to control, to ghrelin alone (in cells of both sexes) and to naltrexone alone (in male cells only). Conclusion.The results suggest that opioids and ghrelin may control LH secretion in carp acting synergistically, probably through the same receptor type. The concept of opioid and ghrelin interaction in the gonadal steroid feedback on LH release is also discussed.

show abstract

Evaluation of progesterone and 20-oxo-progestagens in the plasma of Asian (Elephas maximus) and African (Loxodonta africana) elephants

Schwarzenberger

Strauss

Hoppen³

et al. 1997

Zoo Biol.

View full text Add to dashboard Cite

The corpus luteum of African elephants produces high amounts of 5α‐reduced progesterone metabolites (5α‐pregnane‐3,20‐dione and 5‐α‐pregnane‐3α‐ol‐20‐one), whereas progesterone itself is quantitatively less important, and plasma levels of progesterone during the estrous cycle in elephants are considerably lower than those of other mammals. The objective of this study was to compare the concentration of progesterone in plasma of Asian and African elephants as determined by specific progesterone assays with those of total immunoreactive progestagens containing a 20‐oxo‐group (20‐oxo‐P). These metabolites were determined by an enzyme immunoassay using an antibody against 5‐α‐pregnane‐3β‐ol‐20‐one, 3HS:BSA. Plasma of non‐pregnant Asian (n = 4) and African (n = 4) elephants was collected at weekly intervals for periods of 8–15 months and at random intervals during pregnancy in one Asian elephant. High‐performance liquid chromatography separation of plasma samples of both species demonstrated that in the 20‐oxo‐P assay, 5α‐pregnane‐3,20‐dione makes up ˜60% of the total immunoreactive material. The progesterone and 20‐oxo‐P values during the estrous cycle showed a parallel pattern and were significantly correlated (P < 0.001; Asian: r = 0.80; y = 3.76 × –0.10; African: r = 0.75; y = 2.66 × –0.08). Progesterone and 20‐oxo‐P values in Asian and African elephants were <0.15 ng/ml during the follicular phase (weeks –4 to 0) of the estrous cycle; progesterone values during the luteal phase (weeks 2–9) were 0.60 ± 0.03 and 0.53 ± 0.03 ng/ml, and the 20‐oxo‐P values were 2.19 ± 0.16 and 1.48 ± 0.12 ng/ml, respectively. The 20‐oxo‐P values of the pregnant animal, although slightly higher, were comparable to those of non‐pregnant elephants during the luteal phase. Total immunoreactive 20‐oxo‐P values are about three times higher than those of progesterone during the luteal phase, and 5α‐pregnane‐3,20‐dione is the major immunoreactive 20‐oxo‐P in the plasma of Asian and African elephants. Zoo Biol 16:403–413, 1997. © 1997 Wiley‐Liss, Inc.

show abstract

Inhibition of gonadotrophin release in mares during the luteal phase of the oestrous cycle by endogenous opioids

Cited by 55 publications

References 20 publications

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Interaction of ghrelin and opioids in luteinizing hormone (LH) secretion by pituitary cells of common carp, <I>Cyprinus carpio</I> (Actinopterygii: Cypriniformes: Cyprinidae), cultured in vitro

Evaluation of progesterone and 20-oxo-progestagens in the plasma of Asian (Elephas maximus) and African (Loxodonta africana) elephants

Contact Info

Product

Resources

About