Effects of GABA(A) receptor modulation on the expression of GnRH gene and GnRH receptor (GnRH-R) gene in the hypothalamus and GnRH-R gene in the anterior pituitary gland of follicular-phase ewes

Effect of central administration of indomethacin on anandamide-induced GnRH/LH secretion in the hypothalamus of anoestrous ewes

Introduction

It is suggested that cannabinoids (CBs) may disturb reproduction through action on hypothalamic gonadotropin-releasing hormone (GnRH) neurons directly or indirectly through intermediates such as prostaglandins. The study aimed to determine the influence of intracerebroventricular (i.c.v.) injection of the endogenous cannabinoid anandamide (N-arachidonoylethanolamine - AEA), alone or with the prostaglandin synthesis inhibitor indomethacin (IND), on GnRH/luteinising hormone (LH) secretion. The purpose of the research was to clarify the role of endocannabinoids and their interaction with prostaglandins in the regulation of reproduction at the level of the hypothalamus and pituitary in anoestrous sheep.

Material and Methods

The study was performed on 24 anoestrous ewes divided into four experimental groups: a control group receiving i.c.v. injection of Ringer-Locke solution, an AEA group that received i.c.v. injection of 30 μM of AEA, an IND group receiving i.c.v. injection of 5 μM of IND and an AEA + IND group that received i.c.v. injections of 30 μM of AEA and 5 μM of IND.

Results

Anandamide stimulated GnRH protein and gene expression in the median eminence and protein expression in the preoptic area without influencing GnRH messenger RNA (mRNA) in this structure. Indomethacin reversed the changes in GnRH secretion after AEA administration. It was also found that AEA stimulated LH mRNA in the pituitary without influencing LH release.

Conclusion

Our results support the role of endogenous cannabinoids in the regulation of reproductive processes at the central nervous system level. They may act directly on the hypothalamic GnRH neurons or indirectly through intermediates such as prostaglandins.

Vitamin K in Vertebrates' Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species

Vitamin K (VK) is a fat-soluble vitamin that vertebrates have to acquire from the diet, since they are not able to de novo synthesize it. VK has been historically known to be required for the control of blood coagulation, and more recently, bone development and homeostasis. Our understanding of the VK metabolism and the VK-related molecular pathways has been also increased, and the two main VK-related pathways-the pregnane X receptor (PXR) transactivation and the co-factor role on the γ-glutamyl carboxylation of the VK dependent proteins-have been thoroughly investigated during the last decades. Although several studies evidenced how VK may have a broader VK biological function than previously thought, including the reproduction, little is known about the specific molecular pathways. In vertebrates, sex differentiation and gametogenesis are tightly regulated processes through a highly complex molecular, cellular and tissue crosstalk. Here, VK metabolism and related pathways, as well as how gametogenesis might be impacted by VK nutritional status, will be reviewed. Critical knowledge gaps and future perspectives on how the different VK-related pathways come into play on vertebrate's reproduction will be identified and proposed. The present review will pave the research progress to warrant a successful reproductive status through VK nutritional interventions as well as towards the establishment of reliable biomarkers for determining proper nutritional VK status in vertebrates.

Effects of Stachys sylvatica hydroalcoholic extract on the ovary and hypophysis-gonadal axis in a rat with polycystic ovary syndrome

Background

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting women. The purpose of this study is to evaluate the effects of Stachys sylvatica hydroalcoholic extract on biochemical and histological parameters in a rat model of polycystic ovary syndrome. Thirty adult female Wistar rats with an average weight of 180 g were divided into five groups of six rats. Animals were divided into groups of control, PCOS (intramuscular injection of 2 mg estradiol valerate, Aburaihan Co., Iran/rat, once), and treated with hydroalcoholic extract of Stachys sylvatica. After 60 days of PCOS induction, 100, 250, and 500 mg/kg BW Stachys sylvatica hydroalcoholic extract were injected intraperitoneally. The control group was just injected with olive oil as a solvent. After 10 days of treatment, animals were weighed and then sacrificed and blood samples were taken from their heart for hormonal studies. Ovaries of all groups were cut for histological studies and fixed in formaldehyde, and 7-μm sections were prepared by microtome and stained using hematoxylin–eosin. The data were analyzed by one-way ANOVA and Tukey-Kramer post hoc test with the SPSS software. The significant level was p < 0.05.

Results

The Stachys sylvatica extract can improve obesity in the PCOS group. The histological and hormonal results showed that PCOS induction can decrease the number of preantral, antral, and Graafian follicles as well as corpus luteum in comparison with the control (p < 0.001), whereas the number of cystic follicles increased significantly (p < 0.001). After treatment with Stachys sylvatica hydroalcoholic extract (500 mg/kg), a significant increase was observed in all these parameters. In addition, the number of cystic follicles decreased significantly (p < 0.001). The level of LH and FSH hormones decreased significantly (p < 0.01) in the PCOS group compared with the control. In contrast, the estrogen level increased significantly (p < 0.01). In the 250 and 500 mg/kg group, treatment with the extract could increase FSH and decrease estrogen concentration significantly relative to the PCOS group (p < 0.01). Results of antral follicle morphometry indicated an increase in follicle diameter and theca thickness, but the thickness of the granulosa layer decreased significantly. An improvement in these measurements was observed in the treated PCOS groups with all doses.

Conclusions

It can be concluded that Stachys sylvatica hydroalcoholic extract can improve some symptoms of polycystic ovary syndrome because of components such as iridoids, flavonoids, and sesquiterpenes with antioxidant and anti-inflammatory effects. In this experiment, 500 mg/kg dose of extract was considered as the most effective dose.

Stimulatory effect of dopamine derivative, salsolinol, on pulsatile luteinizing hormone secretion in seasonally anestrous sheep: Focus on dopamine, kisspeptin and gonadotropin-releasing hormone

In the present study, there was testing of the hypothesis that a centrally administered dopamine (DA) derivative, salsolinol, could affect pulsatile luteinizing hormone (LH) secretion in seasonally anestrous sheep by affecting the neuronal components of the estradiol (E2) negative feedback. In two experiments performed during early spring (increasing day length - March/April), salsolinol or Ringer-Locke solution (control) were administered into the third brain ventricle (IIIv): 1) in several injections for three consecutive days; and 2) in several hour-long infusions. In addition to determining the LH concentration (in both experiments), the abundances of gonadotropin-releasing hormone (GnRH) and kisspeptin mRNA were examined in the hypothalamus and LHβ subunit mRNA in the pituitary (Experiment 1). In Experiment 2, concentrations of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined in perfusates collected from the infundibular nucleus/median eminence (IN/ME) by the push-pull method. In both experiments, salsolinol increased both LH pulse frequency (P < 0.05) and plasma LH concentration (P < 0.001) compared to controls. The injected salsolinol also increased (P < 0.05) the abundance of GnRH mRNA in the mediobasal hypothalamus and kisspeptin mRNA in the arcuate nucleus. The two doses of infused salsolinol decreased DA to undetectable concentrations and DOPAC concentration by 60% in perfusates collected from the IN/ME. In conclusion, exogenous salsolinol functioning centrally stimulates pulsatile LH secretion in sheep during seasonal anestrus. It is suggested that salsolinol may have this effect by reducing the activity of the hypothalamic neuroendocrine dopaminergic system, which results in an increase in both kisspeptin and GnRH neurons activity.

Does kisspeptin participate in GABA-mediated modulation of GnRH and GnRH receptor biosynthesis in the hypothalamic-pituitary unit of follicular-phase ewes?

BACKGROUND

The inverse relationship between GnRH transcript level and GABA neurons activity has suggested that GABA at the hypothalamic level may exert a suppressive effect on subsequent steps of the GnRH biosynthesis. In the present study, we analyzed the effects of GABA type A receptor agonist (muscimol) or antagonist (bicuculline) on molecular mechanisms governing GnRH/LH secretion in follicular-phase sheep.

METHODS

ELISA technique was used to investigate the effects of muscimol and/or bicuculline on levels of post-translational products of genes encoding GnRH ligand and GnRH receptor (GnRHR) in the preoptic area (POA), anterior (AH) and ventromedial (VMH) hypothalamus, stalk/median eminence (SME), and GnRHR in the anterior pituitary (AP). Real-time PCR was chosen for determination of the effect of drugs on kisspeptin (Kiss 1) mRNA level in POA and VMH including arcuate nucleus (VMH/ARC), and on Kiss1 receptor (Kiss1r) mRNA abundance in POA-hypothalamic structures. These analyses were supplemented by RIA method for measurement of plasma LH concentration.

RESULTS

The study demonstrated that muscimol and bicuculline significantly decreased or increased GnRH biosynthesis in all analyzed structures, respectively, and led to analogous changes in plasma LH concentration. Similar muscimol- and bicuculline-related alterations were observed in levels of GnRHR. However, the expression of Kiss 1 and Kiss1r mRNAs in selected POA-hypothalamic areas of either muscimol- and bicuculline-treated animals remained unaltered.

CONCLUSIONS

Our data suggest that GABAergic neurotransmission is involved in the regulatory pathways of GnRH/GnRHR biosynthesis and then GnRH/LH release in follicular-phase sheep conceivably via indirect mechanisms that exclude involvement of Kiss 1 neurons.

The effects of 6-Gingerol on reproductive improvement, liver functioning and Cyclooxygenase-2 gene expression in estradiol valerate - Induced polycystic ovary syndrome in Wistar rats

6-Gingerol is the major pungent ingredient of ginger with anti-inflammatory and antioxidant properties. In this study, we evaluate the effects of 6-gingerol on the biochemical parameters and ovarian histological improvements in estradiol valerate (EV) induced PCOS rats. Thirty six female Wistar rats were divided into 4 groups: control, received normal diet, PCOS control, received 4 mg/kg EV injection for 28 days and two experimental groups, received an EV injection for 28 days and followed by 6-gingerol (200 μg/_kg and 400 μg/_kg) for 14 days. The administration of EV led to increase body and ovarian weights, abnormality in serum sex steroid profile, decrease in antioxidant activity and increase in COX-2 gene expression. 6-gingerol treatments, particularly the 400 μg/_kg dose, markedly attenuated these alterations. 6-gingerol showed beneficial effects in the EV induced PCOS rats via decreased expression of COX-2, restored biochemical parameters to normal and decreased of cysts in the ovaries.

Neuroendocrine regulation of GnRH release and expression of GnRH and GnRH receptor genes in the hypothalamus-pituitary unit in different physiological states

This review is focused on the relationship between neuroendocrine regulation of GnRH/LH secretion and the expression of GnRH and GnRH receptor (GnRHR) genes in the hypothalamic-pituitary unit during different physiological states of animals and under stress. Moreover, the involvement of hypothalamic GABA-ergic, Beta-endorphinergic, CRH-ergic, noradrenergic, dopaminergic and GnRH-ergic systems in the regulation of expression of the GnRH and GnRHR genes as well as secretion of GnRH/LH is analyzed. It appears that the neural mechanisms controlling GnRH gene expression in different physiological states may be distinct from those regulating GnRH/LH release. The hypothalamic GnRHR gene is probably located in different neural systems and may act in a specific way on GnRH gene expression and GnRH release.