Luteinizing Hormone Secretion Research Articles

Revolutionizing Infertility Management through Novel Peptide-based Targets.

Around 48 million couples and 186 million people worldwide have infertility; of these, approximately 85% have an identifiable cause, the most common being ovulatory dysfunctions, male infertility, polycystic ovary syndrome, and tubule disease. The remaining 15% have infertility for unknown reasons, including lifestyle and environmental factors. The regulation of the hypothalamic- pituitary-adrenal axis (HPA) is crucial for the secretion of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH), which are essential for female reproductive functions. GnRH is the primary reproductive axis regulator. The pattern of GnRH, FSH, and LH release is determined by its pulsatile secretion, which in turn controls endocrine function and gamete maturation in the gonads. Peptides called Kisspeptin (KP), Neurokinin-B (NKB), and Orexin influence both positive and negative feedback modulation of GnRH, FSH, and LH secretion in reproduction. This review article mainly focuses on the historical perspective, isoform, and signaling pathways of KP, NKB, and Orexin novel peptide-based targets including clinical and preclinical studies and having a promising effect in the management of infertility.

Erratum: McCosh et al., "Norepinephrine Neurons in the Nucleus of the Solitary Tract Suppress Luteinizing Hormone Secretion in Female Mice".

Erratum: McCosh et al., "Norepinephrine Neurons in the Nucleus of the Solitary Tract Suppress Luteinizing Hormone Secretion in Female Mice".

Role of Membrane Estrogen Receptor Alpha on the Positive Feedback of Estrogens on Kisspeptin and GnRH Neurons.

Estrogens act through nuclear and membrane-initiated signaling. Estrogen receptor alpha (ERα) is critical for reproduction, but the relative contribution of its nuclear and membrane signaling to the central regulation of reproduction is unclear. To address this question, two complementary approaches were used: estetrol (E4) a natural estrogen acting as an agonist of nuclear ERs, but as an antagonist of their membrane fraction, and the C451A-ERα mouse lacking mERα. E4 dose- dependently blocks ovulation in female rats, but the central mechanism underlying this effect is unknown. To determine whether E4 acts centrally to control ovulation, its effect was tested on the positive feedback of estradiol (E2) on neural circuits underlying luteinizing hormone (LH) secretion. In ovariectomized females chronically exposed to a low dose of E2, estradiol benzoate (EB) alone or combined with progesterone (P) induced an increase in the number of kisspeptin (Kp) and gonadotropin-releasing hormone (GnRH) neurons coexpressing Fos, a marker of neuronal activation. E4 blocked these effects of EB, but not when combined to P. These results indicate that E4 blocked the central induction of the positive feedback in the absence of P, suggesting an antagonistic effect of E4 on mERα in the brain as shown in peripheral tissues. In parallel, as opposed to wild-type females, C451A-ERα females did not show the activation of Kp and GnRH neurons in response to EB unless they are treated with P. Together these effects support a role for membrane-initiated estrogen signaling in the activation of the circuit mediating the LH surge.

7940 Is Urocortin 2 A Mediator Of Stress-induced Suppression Of The Luteinizing Hormone Surge?

Abstract Disclosure: H.F. Bell: None. R.A. Carrasco: None. M.J. Kreisman: None. R.B. McCosh: None. K.M. Breen Church: None. Stress is thought to be a contributing factor to the reduction of reproductive function and infertility observed in many different species. Although this is a well-documented phenomenon, the neural mechanisms mediating the suppression of reproductive neuroendocrine activity in response to stress are not yet fully understood. The paraventricular nucleus (PVN) of the hypothalamus is an integral part of the neural response to stress. The PVN initiates activation of Corticotropin Releasing Hormone (CRH) neurons and, in addition to CRH, the PVN contains a population of neurons expressing Urocortin 2 (UCN2), a CRH-like family member, with high affinity for CRH receptor 2. In females, stress has been shown to inhibit both the pulse and surge modes of Luteinizing Hormone (LH) secretion. We have preliminary evidence that kisspeptin neurons, controlling either type of LH secretion, contain CRH receptor 2. In this study we tested the sufficiency of UCN2 to disrupt the estradiol-induced LH surge. Female mice were ovariectomized and given a high estradiol treatment to induce a circadian-timed LH surge. Two days later, UCN2 or Vehicle was administered into the lateral ventricle via ICV injection on the morning of the expected surge (10 AM). Blood and brains were collected in the evening (6 PM), at the time of the expected surge. Whole blood from the tail tip was measured by LH ELISA and a surge was defined as > 0.5 ng/mL. A majority of saline-treated animals expressed an LH surge (8 of 9 females). In contrast, 0% of UCN2-treated animals surged (n=7), suggesting that UCN2 impaired the positive feedback response to estradiol. Additionally, immunohistochemistry was performed to observe colocalization of c-Fos within Kisspeptin neurons in the rostral periventricular region of the third ventricle (RP3V) which are responsible for surge generation. Lower Kisspeptin/C-Fos co-expression in animals treated with UCN2 demonstrated the efficacy of UCN2 to impair estradiol-induced activation of RP3V Kisspeptin neurons which are critical for LH surge generation. These results support the hypothesis that UCN2 signaling plays a mediatory role in the stress-induced reduction of ovulatory function in the female mouse. Presentation: 6/1/2024

8602 Classical progesterone signaling in kisspeptin neurons is not required for negative feedback regulation of the GnRH pulse generator in mice

Abstract Disclosure: K.M. Dillon: None. D.B. Lohr: None. A.G. Novak: None. A.V. Petriv: None. N.T. Neifert: None. A.M. Moore: None. Mammalian reproductive function depends on the ability of progesterone to suppress pulsatile gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion in a homeostatic negative feedback loop. Impairments in progesterone negative feedback are associated with the development of polycystic ovary syndrome (PCOS), the leading cause of infertility for people with ovaries. Although previous research indicates cells upstream from GnRH neurons expressing the classical progesterone receptor (PR) are required for negative feedback, the identity of these cells and the mechanism by which they reduce GnRH/LH pulsatile secretion remain unclear. In this study, we aimed to address the hypothesis that PR expressed by a neuronal population in the arcuate nucleus expressing Kisspeptin, Neurokinin B, and Dynorphin, recently defined as the GnRH pulse generator, is required for negative feedback regulation of LH pulses. To achieve this, we utilized Cre-lox technology in mice to conditionally delete PR from kisspeptin cells (KPRKO mice) and assessed fecundity, LH pulsatility, and the mRNA expression of KNDy neuropeptides. Female KPRKO mice paired with B6 stud males for 3 months produced significantly fewer litters (p<0.05, n=5) and pups per litter (p<0.05) compared to WT controls (n=5) (students t-tests), recapitulating a previously reported subfertile phenotype in this model. In a separate cohort of animals, serial blood samples were collected every 6 minutes for 2 hours from the tail-tip of habituated WT and KPRKO mice in diestrus (n=6/group) and estrus (n=6/group), and an ultra-sensitive ELISA was used to detect LH pulses. However, compared to WT controls, KPRKO mice did not exhibit any significant changes in total and baseline LH release, pulse frequency or pulse amplitude in either cycle stages (p>0.05, students t-tests). At the completion of serial blood sampling, brains were collected from WT and KPRKO mice and RNAscope in situ hybridization was used to quantify mRNA for kisspeptin (KISS1) and dynorphin (PDYN), which are excitatory and inhibitory to GnRH/LH secretion, respectively. No differences in the number of KISS1- and PDYN-expressing cells or the number of KISS1 and PDYN mRNA transcripts were observed between WT and KPRKO mice (n=4/group, p>0.05, students t-tests). These data suggest that progesterone signaling in kisspeptin cells through PR is not essential for negative feedback regulation of LH pulses and is unlikely to contribute to the infertile phenotype of KPRKO mice. These results suggest that negative feedback may be maintained via non-classical mechanisms or an unidentified PR-positive neuronal population. Presentation: 6/1/2024

Central δ/κ opioid receptor signaling pathways mediate chronic and/or acute suckling-induced LH suppression in rats during late lactation.

In mammals, secretion of tonic (pulsatile) gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) is often suppressed during lactation. Suppression of GnRH/LH pulses in lactating dams is assumed to be caused by suckling stimuli and a chronic negative energy balance due to milk production. The present study aimed to investigate whether the central enkephalin-δ opioid receptor (DOR) signaling mediated the suppression of LH secretion by acute suckling stimuli and/or chronic negative energy balance due to milk production in rats during late lactation when dams were under a heavy energy demand. On postpartum day 16, the number of Penk (enkephalin mRNA)-expressing cells in the arcuate nucleus was significantly higher in lactating rats than in non-lactating control rats. Pulsatile LH secretion was suppressed in rats with chronic suckling or acute 1-h suckling stimuli 6 h after pup removal on day 16 of lactation. Central DOR antagonism significantly increased the mean LH concentrations and the baseline of LH pulses in rats with chronic suckling but not with acute suckling stimuli on day 16 of lactation. Besides, central κ opioid receptor (KOR) antagonism increased the amplitude of LH pulses in rats with the acute suckling stimuli on day 16 of lactation. These results suggest that central DOR signaling mediates the suppression of LH secretion caused by a negative energy balance in rats receiving chronic suckling during late lactation. On the other hand, central KOR signaling likely mediates acute suckling stimuli-induced suppression of LH secretion in rats during late lactation.

Absence of sex differences in diabetes-induced suppression of KNDy neurons in rats.

Diabetes mellitus disturbs kisspeptin-neurokinin B-dynorphin A (KNDy) neurons in the arcuate nucleus (ARC), which regulate pulsatile luteinizing hormone (LH) secretion in both sexes. However, it remains unclear whether a sex-specific association with the negative effects of diabetes on KNDy neurons exists. Therefore, we examined mRNA expression in KNDy neurons of diabetic male and female rats 7 weeks after streptozotocin (STZ) injection using histochemistry. In gonad-intact rats, the numbers of Kiss1 and Pdyn mRNA-expressing cells in the ARC decreased in an STZ-dose-dependent manner; moreover, no sex-dependent association with STZ treatment was observed. In males, plasma LH and sex steroid levels decreased in diabetic rats. Conversely, those of females did not vary significantly between the control and diabetic rats. Kiss1 expression in the anteroventral periventricular nucleus was slightly affected in diabetic animals, but did not exhibit sex-dependent differences. In gonadectomized rats, the numbers of KNDy mRNA-expressing cells in the ARC and plasma LH levels decreased in diabetic male and female rats; however, sex-dependent differences did not exist. These results demonstrated that a sex-specific association with the negative effects of diabetes on KNDy neurons did not exist. Therefore, the stage of diabetes that induces the suppression of the hypothalamus may not vary according to sex.

Expression of the apelin system in the porcine pituitary during the oestrous cycle and early pregnancy and the effect of apelin on LH and FSH secretion

Reproductive success requires considerable energy investment. Research has shown that some adipokines, i.e. the hormones produced in adipose tissue, affect reproductive functions by influencing all structures of the hypothalamic-pituitary-ovarian axis. Apelin is a recently identified member of the adipokine family. To the best of the authors' knowledge, this is the first study to investigate the gene and protein expression of the apelin system (the apelin hormone and the apelin receptor, APJ) in the anterior (AP) and posterior (PP) pituitary lobes of the domestic pig during different phases of the oestrous cycle (days 2 to 3, 10 to 12, 14 to 16, and 17 to 19) and in early pregnancy (days 10 to 11, 12 to 13, 15 to 16, and 27 to 28). It was also assumed that apelin participates in the regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion and influences Akt, MAPK/Erk1/2, and AMPK signalling pathways in the AP during the oestrous cycle. Apelin, APJ mRNAs and proteins were detected in both pituitary lobes. Apelin was identified in gonadotropes, somatotropes, lactotropes, and thyrotropes. The study also revealed that apelin and APJ mRNA/protein levels fluctuate during the oestrous cycle and early gestation. Apelin affects basal, GnRH- and/or insulin-stimulated gonadotropin secretion in some phases of the cycle, as well as the phosphorylation of Akt, MAPK/Erk1/2, and AMPK proteins in AP cells. These findings suggest that apelin may be produced locally in the pituitary and that this gland is receptive to apelin's action. The study also suggest that apelin may influence female reproductive functions by controlling the release of LH and FSH from AP cells, and that it affects Akt, MAPK/Erk1/2, and AMPK signalling pathways.

Chemogenetic Activation of RFRP Neurons Reduces LH Pulse Frequency in Female but not Male Mice.

The neuropeptide RFRP-3 (RFamide-related peptide-3) is thought to play a role in the negative regulation of fertility. However, the exogenous administration of RFRP-3 yields varying results depending on the dose and route of administration, sex of the subject, and many other variables. Manipulation of in vivo neuronal activity using DREADDs (designer receptor exclusively activated by designer drugs) technology enables investigation of cell type-specific neuronal activation in a manner that better reflects endogenous neuronal activity. To test the effects of RFRP neuronal activation on pulsatile luteinizing hormone (LH) secretion. We generated mice expressing the stimulatory hM3Dq designer receptor exclusively in RFRP cells using 2 different Cre-loxP-mediated approaches: (1) we bred mice to express hM3Dq in all Rfrp-Cre-expressing cells, including some that transiently expressed Rfrp-Cre neonatally (RFRP × hM3Dq mice), and (2) we stereotaxically injected Cre-dependent hM3Dq into the dorsomedial nucleus of RFRP-Cre mice to drive hM3Dq expression exclusively in a subpopulation of adult Rfrp-Cre neurons (RFRP-AAV-hM3Dq mice). We then investigated the effects of acute hM3Dq activation on LH pulse frequency in RFRP × hM3Dq mice, RFRP-AAV-hM3Dq mice, and their respective controls. In both female RFRP × hM3Dq and RFRP-AAV-hM3Dq mice, chemogenetic activation of Cre-driven hM3Dq led to a significant 35% to 50% reduction in LH pulse frequency compared with controls, while no differences in pulse amplitude or mean LH concentration were observed. In marked contrast, RFRP activation did not cause any changes to LH pulse dynamics in male mice. These data show for the first time that activation of neurons that have expressed Rfrp, or of a subset of adult RFRP neurons, can independently suppress LH pulsatility in female, but not male mice.

Effect of repeated low doses of gonadotropin-releasing hormone on the secretion of luteinizing hormone and follicle-stimulating hormone, and ovarian function in dairy cows suffering from anovulation type I

The aim of the study was to evaluate the effect of repeated low doses of gonadotropin-releasing hormone (GnRH) agonist buserelin once a day for 5 days on follicle-stimulating hormone (FSH) and luteinizing hormone (LH) release, and ovarian function in dairy cows with anovulation type I. The study was conducted on 10 anovulatory Polish Holstein-Friesian cows. Cows in Group 1 (n = 5) received 4 µg of buserelin intramuscularly. once a day for 5 days. Control cows from Group 2 (n = 5) received saline. Concentrations of progesterone, FSH, and LH in the blood were analysed using radioimmunoassay (RIA). Ovarian structures were monitored weekly after the end of treatment by ultrasound for 4 weeks. Injections of buserelin increased FSH and LH concentrations. Release of FSH and LH was largely variable, but there was significant (P < 0.001) interaction between time and treatment during all treatment days. The number of follicles in the treatment group was significantly greater (P = 0.029) than in the control group on day 5, the diameter of follicles on day 12 was also larger (P < 0.01) in treated than in control cows. Ovulation occurred in 4 of the 5 treated cows, but only in 1 of the control cows in the 40 days after treatment. In conclusion, repeated low doses of GnRH analogue buserelin once a day for 5 days may increase the concentration of FSH and LH in dairy cows with anovulation type I.

Asiaticoside ameliorates uterine injury induced by zearalenone in mice by reversing endometrial barrier disruption, oxidative stress and apoptosis

Zearalenone (ZEA) is a mycotoxin produced by Fusarium fungi that has been shown to have adverse effects on human and animal health, particularly on the fertility of females. As a saponin derived from the medicinal plant Centella asiatica, asiaticoside (AS) has multiple bioactivities. This study aimed to investigate the protective effects of AS on ZEA-induced uterine injury and the underlying mechanism. In the present study, we demonstrated that AS could rescue ZEA-induced uterine histopathological damage and modulate the secretion of sex hormones, including progesterone (P4), luteinizing hormone (LH), and estradiol (E2), in ZEA-treated mice. Moreover, AS alleviated ZEA-induced damage to endometrial barrier function by upregulating the expression of tight junction proteins (ZO-1, occludin, and claudin-3). Further mechanistic investigations indicated that ZEA reduces the antioxidant capacity of uterine tissues, whereas AS improves the antioxidant capacity through activating the Nrf2 signaling pathway. Most notably, the protective effect of AS was blocked in Nrf2 gene knockout (Nrf2−/−) mice. Moreover, the p38/ERK MAPK pathway has been implicated in regulating ZEA toxicity and the beneficial effect of AS. Additionally, an Nrf2 inhibitor (ML385) weaken the suppressive effect of AS on the oxidative stress and MAPK pathway. AS also inhibits ZEA-induced apoptosis in uterine tissues via the PI3K/Akt signaling pathway. However, when the PI3K small molecule inhibitor LY294002 was co-administered, the ability of AS to suppress the expression of apoptosis-related proteins and inhibit ZEA-induced apoptosis decreased. Collectively, these findings reveal the involvement of multiple pathways and targets in the protective effect of AS against ZEA-induced uterine injury, providing a new perspective for the application of AS and the development of a ZEA antidote.

Low concentrations of the food contaminant Deoxynivalenol trigger apoptosis and impair GnRH-induced LH secretion in pituitary gonadotrope-like cells.

AbstractTheFusariummycotoxin deoxynivalenol (DON) is one of the most frequently occurring food contaminants. Nearly all individuals are exposed to DON, due to it widespread presence in grains and grain-based products. Chronic DON poisoning is associated with growth retardation, immunotoxicity as well as impaired reproduction and fetal development. At the molecular level, DON alters intracellular signaling by activating mitogen-activated protein kinases (MAPKs) that modulate cell growth, differentiation, and apoptosis. Of note, these MAPKs are also critical mediators of gonadotrophin-releasing hormone (GnRH)-induced synthesis and secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by pituitary gonadotrope cells. So far, no research has explored the potential endocrine-disrupting effects of DON on pituitary gonadotropins production. Herein, we show the first evidence that DON affects LH production by the immortalized gonadotrope-like cell line LβT2 in a concentration-dependent manner. Taken together, our experiments demonstrated that low concentrations of DON affect GnRH-induced signaling through a mechanism that, at least in part, involves apoptosis and inhibition of GnRH-induced phosphorylation of ERK-MAPK. Consequently, DON also affects the GnRH-induced expression ofCgaandLhb, two critical genes for LH synthesis and secretion by gonadotrope cells in mammals. This research broadens our knowledge of the toxicity of DON and brings a new depth to the potential neuroendocrine implications for reproduction.Graphical abstract

Previous illicit androgen users display persistently impaired Leydig cell capacity but recovered luteinising hormone secretion

Previous illicit androgen users display persistently impaired Leydig cell capacity but recovered luteinising hormone secretion

ZEB1 Inhibits LHβ Subunit Transcription When Overexpressed, but Is Dispensable for LH Synthesis in Mice.

Luteinizing hormone (LH), a heterodimeric glycoprotein produced by pituitary gonadotrope cells, regulates gonadal function. Hypothalamic gonadotropin-releasing hormone (GnRH) stimulates LH synthesis and secretion. GnRH induces LHβ subunit (Lhb) expression via the transcription factor, early growth response 1 (EGR1), acting on the Lhb promoter. In contrast, overexpression of zinc finger E-box binding homeobox 1 (ZEB1) represses LH production in mice, but the underlying mechanism was not previously elucidated. Here, we observed that ZEB1 inhibited GnRH-stimulated but not basal Lhb mRNA expression in homologous murine LβT2 cells. Moreover, ZEB1 blocked GnRH and/or EGR1 induction of murine Lhb but not human LHB promoter-reporter activity in these cells. Using chimeric reporters, we mapped the species-specific ZEB1 sensitivity to sequence differences, including in Z- and E-boxes, in the proximal Lhb/LHB promoters, immediately upstream of the transcription start sites. ZEB1 bound to the murine Lhb promoter with higher affinity than to the human LHB promoter in this region. To examine ZEB1's physiological role in LH synthesis, we characterized gonadotrope-specific Zeb1 knockout mice. Loss of ZEB1 in gonadotropes did not affect LH production or secretion. Collectively, the data suggest that ZEB1, when overexpressed, can inhibit GnRH/EGR1 induction of murine Lhb transcription but does not play a necessary role in LH synthesis in mice.

Androgen Inhibition of Reproductive Neuroendocrine Function in Females and Transgender Males.

Ovarian function is controlled by pituitary secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH), which in turn are governed by gonadotropin releasing hormone (GnRH) secreted from the brain. A fundamental principle of reproductive axis regulation is negative feedback signaling by gonadal sex steroids back to the brain to fine-tune GnRH and gonadotropin secretion. Endogenous negative feedback effects can be mimicked by exogenous steroid treatments, including androgens, in both sexes. Indeed, a growing number of clinical and animal studies indicate that high levels of exogenous androgens, in the typically male physiological range, can inhibit LH secretion in females, as occurs in males. However, the mechanisms by which male-level androgens inhibit GnRH and LH secretion still remain poorly understood, and this knowledge gap is particularly pronounced in transgender men (individuals designated female at birth but identifying as male). Indeed, many transgender men take long-term gender-affirming hormone therapy that mimics male-level testosterone levels. The impact of such gender-affirming testosterone on the reproductive axis, both at the ovarian and neuroendocrine level, is a long-understudied area that still requires further investigation. Importantly, the few concepts of androgen actions in females mostly come from studies of polycystic ovary syndrome, which does not recapitulate a similar androgen milieu or a pathophysiology of inhibited LH secretion as occurs in testosterone-treated transgender men. This review summarizes clinical evidence indicating that exogenous androgens can impair neuroendocrine reproductive function in both female individuals and transgender men and highlights emerging experimental data supporting this in recently developed transgender rodent models.

The deletion of nuclear progesterone receptors from kisspeptin cells does not impair negative feedback in female mice.

Reproductive function in mammals depends on the ability of progesterone to suppress pulsatile gonadotrophin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion in a homeostatic negative feedback loop. Previous research identified that cells upstream from GnRH neurons expressing the nuclear progesterone receptor (PGR) are required for progesterone-negative feedback. However, the identity of these cells and the mechanism by which they reduce GnRH/LH pulsatile secretion is unknown. We aimed to address the hypothesis that PGR expressed by a neural population in the arcuate nucleus recently identified as the GnRH pulse generator, cells expressing Kisspeptin, Neurokinin B, and Dynorphin (KNDy cells), mediate progesterone negative feedback. To achieve this, we utilized female mice with the PGR gene conditionally deleted from kisspeptin cells (KPRKO mice) and observed a substantial decrease in the percentage of KNDy neurons co-expressing PGR mRNA (11% in KPRKO mice versus 86% in wildtype mice). However, KPRKO mice did not display changes in the frequency or amplitude of LH pulses in diestrus or estrus, nor in the ability of exogenous progesterone to blunt a post-castration rise in LH. Further, mRNA expression of arcuate kisspeptin and dynorphin, which are excitatory and inhibitory to GnRH secretion, respectively, remained unaltered in KPRKO mice compared to wildtype controls. Together, these findings show that the near-complete loss of PGR signaling from KNDy cells does not impact negative feedback regulation of GnRH pulse generation in mice, suggesting that feedback through this receptor can occur via a small number of KNDy cells or a yet unidentified cell population.

Localization of β-Nerve Growth Factor in the Stallion Reproductive Tract.

β-Nerve growth factor (β-NGF) is a protein produced in the reproductive tract of camelids (camels, llamas, and alpacas) that has been identified as the ovulation inducing factor in seminal plasma. β-NGF from seminal plasma deposited into the reproductive tract of the female camelid acts systemically to stimulate the secretion of luteinizing hormone (LH) from the anterior pituitary, which in turn induces follicle maturation and ovulation. The objectives of the present study were to determine if β-NGF is present in the reproductive tract of the stallion and identify the specific site(s) of production. The hypotheses were that β-NGF would be present in the stallion reproductive tract and would primarily be localized in Sertoli cells of the testes and the prostate gland. Immunohistochemistry on paraffin-embedded paraformaldehyde-fixed tissues was performed using a rabbit polyclonal anti-β-NGF antibody on a total of six male equine reproductive tracts, including a one-day old colt, a one-year-old colt, and four adult stallion tracts. Strong immunostaining was observed in the efferent ducts of the testes and the epithelial cells of the prostate, seminal vesicles, bulbourethral glands, and ampullae. Weaker β-NGF staining was noted in Leydig cells, Sertoli cells, and spermatogonia within the testes and in epithelial cells of the epididymis. In conclusion, immunohistochemistry revealed that β-NGF is present in the stallion reproductive tract, and the protein is primarily present in the efferent ducts of the testes and in all accessory sex glands.

Peripheral administration of a κ-opioid receptor agonist nalfurafine inactivates gonadotropin-releasing hormone pulse generator activity in goats

Neurons co-expressing kisspeptin, neurokinin B, and dynorphin A (KNDy neurons), located in the arcuate nucleus (ARC) of the hypothalamus, are indicated to be the gonadotropin-releasing hormone (GnRH) pulse generator. Dynorphin A is reported to suppress GnRH pulse generator activity. Nalfurafine is a selective agonist of the κ-opioid receptor (KOR), a receptor for dynorphin A, clinically used as an anti-pruritic drug. This study aimed to evaluate the effects of nalfurafine on GnRH pulse generator activity and luteinizing hormone (LH) pulses using female goats. Nalfurafine (0, 2, 4, 8, or 16 μg/head) was intravenously injected into ovariectomized Shiba goats. The multiple unit activity (MUA) in the ARC area was recorded, and plasma LH concentrations were measured 2 and 48 h before and after injection, respectively. The MUA volley interval during 0–2 h after injection was significantly increased in the nalfurafine 8 and 16 μg groups compared with the vehicle group. In 0–2 h after injection, the number of LH pulses was significantly decreased in the nalfurafine 8 and 16 μg groups, and the mean and baseline LH were significantly decreased in all nalfurafine-treated groups (2, 4, 8, and 16 μg) compared with the vehicle group. These results suggest that nalfurafine inhibits the activity of the GnRH pulse generator in the ARC, thus suppressing pulsatile LH secretion. Therefore, nalfurafine could be used as a reproductive inhibitor in mammals.

Norepinephrine Neurons in the Nucleus of the Solitary Tract Suppress Luteinizing Hormone Secretion in Female Mice.

Stress impairs fertility, at least in part, via inhibition of gonadotropin secretion. Luteinizing hormone (LH) is an important gonadotropin that is released in a pulsatile pattern in males and in females throughout the majority of the ovarian cycle. Several models of stress, including acute metabolic stress, suppress LH pulses via inhibition of neurons in the arcuate nucleus of the hypothalamus that coexpress kisspeptin, neurokinin B, and dynorphin (termed KNDy cells) which form the pulse generator. The mechanism for inhibition of KNDy neurons during stress, however, remains a significant outstanding question. Here, we investigated a population of catecholamine neurons in the nucleus of the solitary tract (NTS), marked by expression of the enzyme dopamine beta-hydroxylase (DBH), in female mice. First, we found that a subpopulation of DBH neurons in the NTS is activated (express c-Fos) during metabolic stress. Then, using chemogenetics, we determined that activation of these cells is sufficient to suppress LH pulses, augment corticosterone secretion, and induce sickness-like behavior. In subsequent studies, we identified evidence for suppression of KNDy cells (rather than downstream signaling pathways) and determined that the suppression of LH pulses was not dependent on the acute rise in glucocorticoids. Together these data support the hypothesis that DBH cells in the NTS are important for regulation of neuroendocrine and behavioral responses to stress.

Male Body Odor Affects Emotional State, LH, and Cortisol Secretion in Women of Different Age Groups.

Hormone changes across women's menstrual cycles may lead to changes in their perceptions of chemical signals and their hormonal responses to these cues. The aim of the present study was to determine the role of menstrual cycle phase in the response to extracts of male axillary secretions (EMAS) in women. We tested healthy reproductive age and premenopausal women (n = 29). An EMAS/control solution was applied once every two hours during either the follicular or luteal phase, at which point saliva samples for luteinizing hormone (LH) and cortisol monitoring were collected. LH and cortisol concentrations were analyzed using the enzyme immunoassay (EIA) technique. Positive and Negative Affect Schedule (PANAS) and Visual Analogue Scales (VAS) scores were used to assess the participants' moods. For the first time, we showed that EMAS may produce opposite effects on LH secretion depending on the menstrual cycle phase of the recipient. We observed a significant increase in the number of LH peaks (p = 0.0447) and their amplitudes (p = 0.0469) when EMAS was applied during the follicular phase, while the same application in the luteal phase lowered the amplitudes of LH peaks (p = 0.0382). For the first time, we showed that EMAS application increased salivary cortisol levels in reproductive age women relative to premenopausal women (p = 0.0032). PANAS scores revealed changes in positive and negative affect after EMAS application. Our data indicate the significance of the menstrual cycle phase for EMAS' effects on LH secretion and mood, but not on cortisol secretion in women.