Estradiol, a key endocrine signal in the sexual differentiation and activation of reproductive behavior in quail

Jujuboside A Attenuates Polycystic Ovary Syndrome Based on Estrogen Metabolism Through Activating AhR-mediated CYP1A2 Expression

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women. This study aimed to investigate the therapeutic effects and mechanism of Jujuboside A on PCOS using a dehydroepiandrosterone (DHEA)-induced PCOS mouse model. Estrogen and androgen homeostasis was evaluated in serum from both clinical samples and PCOS mice. The stages of the estrous cycle were determined based on vaginal cytology. The ovarian morphology was observed by stained with hematoxylin and eosin. Moreover, we analyzed protein expression of cytochrome P450 1A1 (CYP1A1), cytochrome P450 1A2 (CYP1A2) and aryl hydrocarbon receptor (AhR) in ovary and KGN cells. Molecular docking, immunofluorescence, and luciferase assay were performed to confirm the activation of AhR by Jujuboside A. Jujuboside A effectively alleviated the disturbance of estrogen homeostasis and restored ovarian function, leading to an improvement in the occurrence and progression of PCOS. Furthermore, the protective effect of JuA against PCOS was dependent on increased CYP1A2 levels regulated by AhR. Our findings suggest that Jujuboside A improves estrogen disorders and may be a potential therapeutic agent for the treatment of PCOS.

The effectiveness of Bio-plus2B®, Techno Mos® and their mixture on the rate of egg production, egg characteristics, retention of nutrients and blood metabolites through the early period of production

BACKGROUND

The trend of using probiotic, prebiotic and their mixture as alternative feed additives which works as growth promoters in poultry diets to increase the productive performance and the immunity of the flock still have an importance consideration. So that the aim of this study is to estimate the impact of Bio-plus2B® (probiotic), Techno Mos® (prebiotic) or their mixture (synbiotic) on egg production, egg and shell quality, some blood metabolites and retention of nutrients between 28 and 40 weeks of age. The hens (ISA brown laying) were allocated randomly in 40 cages; 10 cages/treatment with two hens each. The treatments were the control (T1), T2 (Probiotic: 1 g Bio-plus2B® (Bacillus licheniformis plus Bacillus subtilis)/kg feed), T3 (Prebiotic: 1 g Techno Mos® (Mannanoligosaccarides (MOS) and 1,3 B-glucan) /kg feed) and T4 (Synbiotic: 1 g Bio-plus2B® plus 1 g Techno Mos®/ kg feed).

RESULTS

Hen-day egg production% and mass were significantly increased (P < 0.05) with T2 and T4 treatments. The experimental treatments recorded an increase in albumen index, Haugh unit (P < 0.01), shell thickness (P < 0.05), the retention of crude protein (CP), crude fiber (CF) and ether extract (EE) (P < 0.05), plasma globulin, albumin and total protein (P < 0.001) versus to the untreated group, while egg weight was not affected. Synbiotic treatment showed a significant (P < 0.001) increase in shell calcium content. T3 and T4 treatments were significantly decreased plasma cholesterol (P < 0.001) and low density lipoprotein (LDL) (P < 0.05). Alanine transaminase (ALT) was significantly (P < 0.001) decreased and estradiol hormone was increased (P < 0.001) in the experimental groups versus to the control.

CONCLUSIONS

It concluded that adding probiotic and/or prebiotic in the early age laying hens diets had beneficial effects for productivity with improving the egg shell thickness.

Impacts of selenium nanoparticles and spirulina alga to alleviate the deleterious effects of heat stress on reproductive efficiency, oxidative capacity and immunity of doe rabbits

Effects of dietary inclusion of spirulina platensis (SP) and selenium nanoparticles (SeNPs) combination (SP-SeNPs) on the reproductive performance in vivo and in vitro, reproductive and metabolic hormones, hemato-bichemical parameters, oxidative stress, and immunity of heat-stressed doe rabbis were evaluated. All supplements significantly increased live litter size at birth and weaning, viability rate at birth, hemoglobin and red blood cells, and plasma T3, T4, insulin, total proteins and albumin compared with control. Plasma estradiol 17-β (pre-mating), progesterone (mid-pregnancy), and prolactin (day -7 postpartum) were significantly increased only by SeNPs (0.3, 0.4, and 0.5 mg/kg). All dietary supplements significantly reduced WBCs, cortisol, lipid profile, and improved liver and kidney functions. Immunoglobulins levels, antioxidants capacity were significantly increased, superoxide dismutase was increased by SeNPs (0.4 and 0.5 mg/kg), while malondialdehyde was reduced by 0.3, 0.4 and 0.5 SeNPs mg/kg. Sexual receptivity, pregnancy rate, viability rate at weaning, ovulation rate, and embryo quality were significantly increased by increasing SeNPs above 0.1 mg, while embryo yield was increased by >0.2 mg SeNPs/kg. A combination of SP and SeNPs, could be potentially used as a strong antioxidant to enhance heat regulation and doe rabbit reproduction via improving reproductive and metabolic hormones, antioxidant status and immunological parameters.

Overview of Avian Sex Reversal

Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics adopt either male or female developmental patterns. In birds, although genetic factors control the sex determination program, sex differentiation is sensitive to hormones, which can induce sex reversal when disturbed. Although these sex-reversed birds can form phenotypes opposite to their genotypes, none can experience complete sex reversal or produce offspring under natural conditions. Promising evidence indicates that the incomplete sex reversal is associated with cell autonomous sex identity (CASI) of avian cells, which is controlled by genetic factors. However, studies cannot clearly describe the regulatory mechanism of avian CASI and sex development at present, and these factors require further exploration. In spite of this, the abundant findings of avian sex research have provided theoretical bases for the progress of gender control technologies, which are being improved through interdisciplinary co-operation and will ultimately be employed in poultry production. In this review, we provide an overview of avian sex determination and differentiation and comprehensively summarize the research progress on sex reversal in birds, especially chickens. Importantly, we describe key issues faced by applying gender control systems in poultry production and chronologically summarize the development of avian sex control methods. In conclusion, this review provides unique perspectives for avian sex studies and helps scientists develop more advanced systems for sex regulation in birds.

New cells added to the preoptic area during sex change in the common clownfish Amphiprion ocellaris

Sex differences in cell number in the preoptic area of the hypothalamus (POA) are documented across all major vertebrate lineages and contribute to differential regulation of the hypothalamic-pituitary-gonad axis and reproductive behavior between the sexes. Sex-changing fishes provide a unique opportunity to study mechanisms underlying sexual differentiation of the POA. In anemonefish (clownfish), which change sex from male to female, females have approximately twice the number of medium-sized cells in the anterior POA compared to males. This sex difference transitions from male-like to female-like during sex change. However, it is not known how this sex difference in POA cell number is established. This study tests the hypothesis that new cell addition plays a role. We initiated adult male-to-female sex change in 30 anemonefish (Amphiprion ocellaris) and administered BrdU to label new cells added to the POA at regular intervals throughout sex change. Sex-changing fish added more new cells to the anterior POA than non-changing fish, supporting the hypothesis. The observed effects could be accounted for by differences in POA volume, but they are also consistent with a steady trickle of new cells being gradually accumulated in the anterior POA before vitellogenic oocytes develop in the gonads. These results provide insight into the unique characteristics of protandrous sex change in anemonefish relative to other modes of sex change, and support the potential for future research in sex-changing fishes to provide a richer understanding of the mechanisms for sexual differentiation of the brain.

D2 receptor antagonism enhances cocaine-induced behavioral sensitization in female, but not male Japanese quail ( Coturnix japonica )

Sex differences in cocaine-induced behaviors are well established. In rodents, females show enhanced locomotion to cocaine over multiple trials compared with males, a behavioral response known as sensitization. Estradiol enhances cocaine-induced sensitization in female rats by agonizing dopaminergic activity within the brain. In female quail, cocaine does not increase locomotion regardless of increased estradiol. A higher D2:D1 dopamine receptor ratio in quail compared with rodents may explain this sex and species difference. The goal of the present work was to investigate the role of D2 receptors in cocaine-induced locomotion and sensitization in Japanese quail and to determine whether a greater D2 receptor availability contributed to the lack of cocaine-induced sensitization in female quail found in previous studies. Male and female quail were administered 0, 0.03, 0.05, or 0.07 mg/kg of eticlopride (Eti) followed by 10 mg/kg of cocaine or saline then immediately placed in open-field chambers. Distance traveled was recorded for 30 min daily for 7 days. In female quail, cocaine-induced sensitization was observed with 0.03 or 0.05 mg/kg Eti, but not in cocaine-only females. In male quail, cocaine-induced sensitization was observed similar to previous research. However, Eti did not enhance cocaine-induced locomotion or produce sensitization in male quail. The D2 receptor likely mediates cocaine's motor stimulating effects in quail. In females, this effect is more pronounced. Since high D2 availability is protective against stimulant abuse, Japanese quail may be a useful model for investigating the role of the D2 receptor in cocaine addiction, but further research is needed.

Female presence does not increase testosterone but still ameliorates sickness behaviours in male Japanese quail

Infections can dramatically modify animal behaviour. The extent of these changes depends on an animal's environment. It has been proposed that testosterone modulates the suppression of behavioural symptoms of sickness under certain reproductive contexts. To further understand the role played by testosterone in modulating sickness behaviours under reproductive contexts, we studied a species, the Japanese quail, in which female exposure rapidly decreases circulating testosterone in males. Males received either an immune challenge (lipopolysaccharide - LPS) or a control injection and their behaviours, mass change and testosterone levels were quantified in the presence or absence of a female. Both the presence of a female and LPS treatment reduced testosterone levels. LPS-treated males maintained in isolation expressed expected sickness behaviours, including increased resting (quantified as crouching) and decreased food and water intake. Despite the reduction in testosterone, when paired with females LPS-treated males showed similar amounts of mating behaviours to controls and reduced crouching. In sum, even under very low levels of testosterone, male quail had reduced sickness behaviours when exposed to females, indicating that testosterone may not be key in modulating sickness behaviours, at least in this species.

Direct Full-Length RNA Sequencing Reveals an Important Role of Epigenetics During Sexual Reversal in Chinese Soft-Shelled Turtle

Sex dimorphism is a key feature of Chinese soft-shelled turtle (Pelodiscus sinensis). The males (M) have higher econosmic value than females (F) due to wider calipash and faster growth. Exogenous hormones like estradiol and methyltestosterone can induce sexual reversal to form new phenotypes (pseudo-female, PF; pseudo-male, PM) without changing the genotype. The possibility of inducing sexual reversal is particularly important in aquaculture breeding, but the underlying biological mechanisms remain unclear. Here we applied a direct RNA sequencing method with ultralong reads using Oxford Nanopore Technologies to study the transcriptome complexity in P. sinensis. Nanopore sequencing of the four gender types (M, F, PF, and PM) showed that the distribution of read length and gene expression was more similar between same-sex phenotypes than same-sex genotypes. Compared to turtles with an M phenotype, alternative splicing was more pronounced in F turtles, especially at alternative 3′ splice sites, alternative 5′ splice sites, and alternative first exons. Furthermore, the two RNA methylation modifications m5C and m6A were differentially distributed across gender phenotypes, with the M type having more modification sites in coding sequence regions, but fewer modification sites in 3′UTR regions. Quantitative analysis of enriched m6A RNAs revealed that the N6-methylated levels of Odf2, Pacs2, and Ak1 were significantly higher in M phenotype individuals, while the N6-methylated levels of Ube2o were reduced after sexual reversal from both M and F phenotypes. Taken together, these findings reveal an important role of epigenetics during sexual reversal in Chinese soft-shelled turtles.

Characterizing seasonal transitions: Breeding-like morphology and behavior during the late non-breeding season in green anole lizards

Seasonally breeding animals, such as green anole lizards (Anolis carolinensis), allow for the examination of the control of reproduction during different reproductive states. During the breeding season, the gonads are large and reproductively active. Following the breeding season, gonads regress and become less active, and the lizards enter a refractory period where breeding is inhibited. After this stage, a post-refractory period occurs during which the lizards are still in a non-breeding state, but environmental changes can trigger the onset of breeding. However, it is unclear what causes these changes in reproductive state and we hypothesized that this may be due to alterations in gonadotropin-releasing hormone (GnRH) signaling. The present study aimed to identify morphological and behavioral differences in GnRH- and saline-injected refractory and post-refractory male anoles when housed under the same non-breeding environmental conditions. We found that post-refractory anoles had increased testicular weight, recrudescence, sperm presence, and reproductive behavior, with no impact of GnRH injection. Renal sex segment size and steroidogenic acute regulatory protein (StAR) mRNA levels did not differ among groups, indicating that testosterone levels likely had not increased in post-refractory lizards. Post-refractory anoles in this study were beginning to transition towards a breeding state without exposure to changing environmental conditions, and GnRH was not necessary for these changes. These data reveal a complex interaction between the activation of breeding, changing environmental conditions, and the underlying physiology regulating reproduction in seasonally breeding lizards. Future studies are needed to further elucidate the mechanisms that regulate this relationship.

Advancing reproductive neuroendocrinology through research on the regulation of GnIH and on its diverse actions on reproductive physiology and behavior

The discovery of gonadotropin-inhibitory hormone (GnIH) in 2000 has led to a new research era of reproductive neuroendocrinology because, for a long time, researchers believed that only gonadotropin-releasing hormone (GnRH) regulated reproduction as a neurohormone. Later studies on GnIH demonstrated that it acts as a new key neurohormone inhibiting reproduction in vertebrates. GnIH reduces gonadotropin release andsynthesis via the GnIH receptor GPR147 on gonadotropes and GnRH neurons. Furthermore, GnIH inhibits reproductive behavior, in addition to reproductive neuroendocrine function. The modification of the synthesis of GnIH and its release by the neuroendocrine integration of environmental and internal factors has also been demonstrated. Thus, the discovery of GnIH has facilitated advances in reproductive neuroendocrinology. Here, we describe the advances in reproductive neuroendocrinology driven by the discovery of GnIH, research on the effects of GnIH on reproductive physiology and behavior, and the regulatory mechanisms underlying GnIH synthesis and release.

Sex- and Developmental Stage-Related Differences in the Hepatic Transcriptome of Japanese Quail (Coturnix japonica) Exposed to 17β-Trenbolone

Endocrine-disrupting chemicals can cause transcriptomic changes that may disrupt biological processes associated with reproductive function including metabolism, transport, and cell growth. We investigated effects from in ovo and dietary exposure to 17β-trenbolone (at 0, 1, and 10 ppm) on the Japanese quail (Coturnix japonica) hepatic transcriptome. Our objectives were to identify differentially expressed hepatic genes, assess perturbations of biological pathways, and examine sex- and developmental stage-related differences. The number of significantly differentially expressed genes was higher in embryos than in adults. Male embryos exhibited greater differential gene expression than female embryos, whereas in adults, males and females exhibited similar numbers of differentially expressed genes (>2-fold). Vitellogenin and apovitellenin-1 were up-regulated in male adults exposed to 10 ppm 17β-trenbolone, and these birds also exhibited indications of immunomodulation. Functional grouping of differentially expressed genes identified processes including metabolism and transport of biomolecules, enzyme activity, and extracellular matrix interactions. Pathway enrichment analyses identified as perturbed peroxisome proliferator-activated receptor pathway, cardiac muscle contraction, gluconeogenesis, growth factor signaling, focal adhesion, and bile acid biosynthesis. One of the primary uses of 17β-trenbolone is that of a growth promoter, and these results identify effects on mechanistic pathways related to steroidogenesis, cell proliferation, differentiation, growth, and metabolism of lipids and proteins. Environ Toxicol Chem 2021;40:2559-2570. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

An updated review on behavior of domestic quail with reference to the negative effect of heat stress

Japanese quail originated from the wildlife environment and was first domesticated in Japan in 1595. Japanese quail has widely distributed in various parts of the world. This bird is characterized by its rapid growth rate, high rate of egg production, much lower space requirements, small size, good reproductive potential, short life cycle, resistance to diseases, early sexual maturity (from 39 to 50 days), better laying ability and shorter time of hatching compared with the different species of poultry. All these characteristics rendered it an excellent laboratory animal and a good economical animal protein source (for both egg and meat). Thermal stress was found to be the major limiting variable in poultry production, directly influencing bird welfare conditions. Previous research showed that heat stress in the production environment, induced by high ambient temperatures, may have a direct detrimental effect on welfare, meat quality, carcass characteristics, productivity, egg mass and egg quality. Furthermore, heat stress directly decreases quails' reproductive performance. As tiny, ground-dwelling birds, quail may appear unable to handle extreme temperatures, yet they have methods of fighting the heat. This review will help in developing and strengthening the core of the quail-based poultry sector. In addition, it provides aggregate information on the characteristics of the quail bird as a production unit in poultry farms as well as being an animal model for laboratory experiments. Also, this review provided deep insight into the domestication process and the impact of heat stress on production characteristics, which altered the domestic or Japanese quail substantially.

Gonadotropin-inhibitory hormone (GnIH): A new key neurohormone controlling reproductive physiology and behavior

The discovery of novel neurohormones is important for the advancement of neuroendocrinology. In early 1970s, gonadotropin-releasing hormone (GnRH), a hypothalamic neuropeptide that promotes gonadotropin release, was identified to be an endogenous neurohormone in mammals. In 2000, thirty years later, another hypothalamic neuropeptide, gonadotropin-inhibitory hormone (GnIH), that inhibits gonadotropin release, was found in quail. GnIH acts via GPR147 and inhibits gonadotropin release and synthesis and reproductive function in birds through actions on GnRH neurons in the hypothalamus and pituitary gonadotrophs. Later, GnIH was found in other vertebrates including humans. GnIH studies have advanced the progress of reproductive neuroendocrinology. Furthermore, recent GnIH studies have indicated that abnormal changes in GnIH expression may cause pubertal disorder and reproductive dysfunction. Here, we describe GnIH discovery and its impact on the progress of reproductive neuroendocrinology. This review also highlights advancement and perspective of GnIH studies on drug development for pubertal disorder and reproductive dysfunction. (149/150).

Key role of estrogen receptor β in the organization of brain and behavior of the Japanese quail

Estrogens play a key role in the sexual differentiation of the brain and behavior. While early estrogen actions exert masculinizing effects on the brain of male rodents, a diametrically opposite effect is observed in birds where estrogens demasculinize the brain of females. Yet, the two vertebrate classes express similar sex differences in the brain and behavior. Although ERα is thought to play a major role in these processes in rodents, the role of ERβ is still controversial. In birds, the identity of the estrogen receptor(s) underlying the demasculinization of the female brain remains unclear. The aim of the present study was thus to determine in Japanese quail the effects of specific agonists of ERα (propylpyrazole triol, PPT) and ERβ (diarylpropionitrile, DPN) administered at the beginning of the sensitive period (embryonic day 7, E7) on the sexual differentiation of male sexual behavior and on the density of vasotocin-immunoreactive (VT-ir) fibers, a known marker of the organizational action of estrogens on the quail brain. We demonstrate that estradiol benzoate and the ERβ agonist (DPN) demasculinize male sexual behavior and decrease the density of VT-ir fibers in the medial preoptic nucleus and the bed nucleus of the stria terminalis, while PPT has no effect on these measures. These results clearly indicate that ERβ, but not ERα, is involved in the estrogen-induced sexual differentiation of brain and sexual behavior in quail.

Discovery of gonadotropin-inhibitory hormone (GnIH), progress in GnIH research on reproductive physiology and behavior and perspective of GnIH research on neuroendocrine regulation of reproduction

Based on extensive studies on gonadotropin-releasing hormone (GnRH) it was assumed that GnRH is the only hypothalamic neurohormone regulating gonadotropin release in vertebrates. In 2000, however, Tsutsui's group discovered gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that inhibits gonadotropin release, in quail. Subsequent studies by Tsutsui's group demonstrated that GnIH is conserved among vertebrates, acting as a new key neurohormone regulating reproduction. GnIH inhibits gonadotropin synthesis and release through actions on gonadotropes and GnRH neurons via GnIH receptor, GPR147. Thus, GnRH is not the sole hypothalamic neurohormone controlling vertebrate reproduction. The following studies by Tsutsui's group have further demonstrated that GnIH has several important functions in addition to the control of reproduction. Accordingly, GnIH has drastically changed our understanding about reproductive neuroendocrinology. This review summarizes the discovery of GnIH, progress in GnIH research on reproductive physiology and behavior and perspective of GnIH research on neuroendocrine regulation of reproduction.

Sex differences and similarities in the neural circuit regulating song and other reproductive behaviors in songbirds

In the 1970s, Nottebohm and Arnold reported marked male-biased sex differences in the volume of three song control nuclei in songbirds. Subsequently a series of studies on several songbird species suggested that there is a positive correlation between the degree to which there is a sex difference in the volume of these song control nuclei and in song behavior. This correlation has been questioned in recent years. Furthermore, it has become clear that the song circuit is fully integrated into a more comprehensive neural circuit that regulates multiple courtship and reproductive behaviors including song. Sex differences in songbirds should be evaluated in the context of the full complement of behaviors produced by both sexes in relation to reproduction and based on the entire circuit in order to understand the functional significance of variation between males and females in brain and behavior. Variation in brain and behavior exhibited among living songbird species provides an excellent opportunity to understand the functional significance of sex differences related to social behaviors.

Testosterone synthesis in the female songbird brain

Decades of work have established the brain as a source of steroid hormones, termed 'neurosteroids'. The neurosteroid neuroestradiol is produced in discrete brain areas and influences cognition, sensory processing, reproduction, neurotransmission, and disease. A prevailing research focus on neuroestradiol has essentially ignored whether its immediate synthesis precursor - the androgen testosterone - is also dynamically regulated within the brain. Testosterone itself can rapidly influence neurophysiology and behavior, and there is indirect evidence that the female brain may synthesize significant quantities of testosterone to regulate cognition, reproduction, and behavior. In songbirds, acoustic communication is regulated by neuroestrogens. Neuroestrogens are rapidly synthetized in the caudomedial nidopallium (NCM) of the auditory cortex of zebra finches in response to song and can influence auditory processing and song discrimination. Here, we examined the in vivo dynamics of NCM levels of the neuroestrogen synthesis precursor, testosterone. Unlike estradiol, testosterone did not appear to fluctuate in the female NCM during song exposure. However, a substantial song-induced elevation of testosterone was revealed in the left hemisphere NCM of females when local aromatization (i.e., conversion to estrogens) was locally blocked. This elevation was eliminated when local androgen synthesis was concomitantly blocked. Further, no parallel elevation was observed in the circulation in response to song playback, consistent with a local, neural origin of testosterone synthesis. To our knowledge, this study provides the first direct demonstration that testosterone fluctuates rapidly in the brain in response to socially-relevant environmental stimuli. Our findings suggest therefore that locally-derived 'neuroandrogens' can dynamically influence brain function and behavior. SIGNIFICANCE STATEMENT: This study demonstrates that androgen synthesis occurs rapidly in vivo in the brain in response to social cues, in a lateralized manner. Specifically, testosterone synthesis occurs within the left secondary auditory cortex when female zebra finches hear male song. Therefore, testosterone could act as a neuromodulator to rapidly shape sensory processing. Androgens have been linked to functions such as the control of female libido, and many steroidal drugs used for contraception, anti-cancer treatments, and sexual dysfunction likely influence the brain synthesis and action of testosterone. The current findings therefore establish a clear role for androgen synthesis in the female brain with implications for understanding neural circuit function and behavior in animals, including humans.

Effect of thymectomy on the female reproductive cycle in neonatal guinea pigs

OBJECTIVE

The appropriate function of the hypothalamic-pituitary-gonadal axis is essential for maintaining proper reproductive function. In female mammals, the hypothalamic-pituitary-gonadal axis regulates reproductive changes that take place in the estrus cycle and are necessary for successful reproduction. This study was conducted to investigate the effect of thymectomy on the estrus cycle in neonatally thymectomized guinea pigs.

METHODS

In this study, 12 female guinea pigs, six thymectomized and six sham-operated, were studied. The effects of neonatal thymectomy at 5-7 days of age on parameters of the reproductive axis were examined in female guinea pigs. Gonadotropin and 17β-estradiol levels were assessed at regular intervals (days 0, 3, 6, 9, 12, and 15) of the estrus cycle, and the time of vaginal opening in the thymectomized and shamoperated guinea pigs was determined.

RESULTS

Significant reductions in gonadotropins and 17β-estradiol levels during estrus cycle were found in neonatally thymectomized female guinea pigs compared to sham-operated guinea pigs.

CONCLUSION

The results of this study underscore the importance of the thymus in the neonatal period for normal female reproductive function.

Genetic Variations of CYP19A1 Gene and Stroke Susceptibility: A Case-Control Study in the Chinese Han Population

OBJECTIVE

This study aimed to explore the association between genetic variations of CYP19A1 and stroke susceptibility in the Chinese Han population.

METHODS

A total of 477 stroke patients and 480 healthy controls were recruited in this study. The genotyping of CYP19A1 polymorphisms (rs4646, rs6493487, rs1062033, rs17601876, and rs3751599) was performed by the Agena MassARRAY platform. Under logistic regression models, we evaluated the associations of CYP19A1 polymorphisms and stroke susceptibility by odds ratio and 95% confidence interval.

RESULTS

Our study showed that rs4646 (codominant: P = 0.020; recessive: P = 0.016) and rs17601876 (allele: P = 0.044; codominant: P = 0.011; dominant: P = 0.009; recessive: P = 0.046) significantly decreased the risk of stroke. In the stratification analysis, rs4646 is associated with decreased stroke risk among the individuals older than 64 years (codominant: P = 0.028; recessive: P = 0.010) and women (codominant: P = 0.029; recessive: P = 0.029), whereas rs1062033 increased stroke risk in the subgroup of age 64 years and younger (recessive: P = 0.042). The rs17601876 polymorphism has a strong relationship with stroke susceptibility, which is age and gender dependent. In haplotype analysis, we found a block (rs17601876 and rs3751599), and Ars17601876Grs3751599 haplotype is related to an increased stroke risk (P < 0.05). In addition, CYP19A1 variations had effects on clinical characteristics.

CONCLUSION

CYP19A1 polymorphisms were significantly associated with stroke susceptibility in the Chinese Han population.

Variability of serum reproductive hormones in cows presenting various reproductive conditions in semi-arid areas of the North West Province, South Africa

Background and Aim:

Hormones play a significant role in supporting reproductive processes. Predisposition to metabolic disorders may result from biological alterations in the neurohormonal system, thus leading to impaired immune function and poor reproductive performance. The aim of this study was to determine the reproductive hormonal profile in cows with reproductive conditions in semi-arid areas of the North West Province, South Africa, to establish possible correlations between different conditions and the hormonal profile.

Materials and Methods:

Blood samples were collected from cows in different communal areas of Mafikeng. Convenience sampling was used to collect samples for the study. Blood samples were collected cows experiencing dystocia (n=50), retained placenta (n=13), downer cow syndrome (n=34), vaginal prolapse (n=16), and abortions (n=69), following cases reported at the Animal Health Hospital of the North-West University, Mafikeng Campus. Descriptive statistics, such as mean and standard deviations, were used to describe the distribution of hormone levels across reproductive conditions. p-value less than the significance level was set at 5% (p<0.05).

Results:

Data obtained revealed significantly higher estradiol in abortion (1122.99±71.99 pg/ml), downer cow syndrome (781.32±135.7 pg/ml), and dystocia (862.09±123.44 pg/ml). Oxytocin (OT) differed significantly in cows with dystocia (370.50±71.66 pg/ml) and abortion (574.73±60.65 pg/ml). Significantly low progesterone (Pg) was observed in abortion (2.45±1.509 ng/ml) and dystocia (8.59±0.402 ng/ml) while increased prostaglandin alpha was observed in cows with vaginal prolapse and abortion.

Conclusion:

The findings highlight an increase in serum estradiol and OT in aborting cows. Low Pg and estradiol in cows with vaginal prolapses and retained placenta were noted. An association was seen between downer cow syndrome and high concentrations of estradiol and Pg. Prostaglandin alpha may increase in cases of vaginal prolapse and abortion. Hormonal alterations were observed and may contribute to the incidences of different reproductive conditions.

Acute neuroestrogen blockade attenuates song-induced immediate early gene expression in auditory regions of male and female zebra finches

Neuron-derived estrogens are synthesized by aromatase and act through membrane receptors to modulate neuronal physiology. In many systems, long-lasting hormone treatments can alter sensory-evoked neuronal activation. However, the significance of acute neuroestrogen production is less understood. Both sexes of zebra finches can synthesize estrogens rapidly in the auditory cortex, yet it is unclear how this modulates neuronal cell signaling. We examined whether acute estrogen synthesis blockade attenuates auditory-induced expression of early growth response 1 (Egr-1) in the auditory cortex of both sexes. cAMP response element-binding protein phosphorylation (pCREB) induction by song stimuli and acute estrogen synthesis was also examined. We administered the aromatase inhibitor fadrozole prior to song exposure and measured Egr-1 across several auditory regions. Fadrozole attenuated Egr-1 in the auditory cortex greater in males than females. Females had greater expression and clustering of aromatase cells than males in high vocal center (HVC) shelf. Auditory-induced Egr-1 expression exhibited a large sex difference following fadrozole treatment. We did not observe changes in pCREB expression with song presentation or aromatase blockade. These findings are consistent with the hypothesis that acute neuroestrogen synthesis can drive downstream transcriptional responses in several cortical auditory regions, and that this mechanism is more prominent in males.

Aromatase immunolocalization and activity in the lizard's brain: Dynamic changes during the reproductive cycle

The purpose of the present study is to highlight the role of aromatase in the neuroendocrine control of the reproductive cycle of the male lizard Podarcis sicula during the three significant phases, i.e. the pre-reproductive, reproductive, and post-reproductive stages. Using immunohistochemical, biochemical, and hormonal tools, we have determined the localization and the activity of P450 aromatase (P450 aro) in the lizard's brain together with the determination of hormonal profile of sex steroids, i.e. testosterone and 17β-estradiol. The present data demonstrated that the localization of P450 is shown in brain regions involved in the regulation of the reproductive behavior (medial septum, preoptic area, and hypothalamus). Its activity, as well as the intensity of the signal, is modified according to the period of reproduction, resulting in functional dynamic changes. P450 aro activity and signal intensity decrease in the pre-reproductive period and progressively increase during the reproductive stage until it reaches the maximum peak level at the post-reproductive phase. P450 aro determines a local estrogen synthesis, balancing the testosterone and estradiol levels, and therefore its role is crucial, since it plays an important role in the neuroendocrine/behavioral regulation of the reproductive processes in the male lizard P. sicula.

How to Contribute to the Progress of Neuroendocrinology: Discovery of GnIH and Progress of GnIH Research

It is essential to discover novel neuropeptides that regulate the functions of pituitary, brain and peripheral secretory glands for the progress of neuroendocrinology. Gonadotropin-releasing hormone (GnRH), a hypothalamic neuropeptide stimulating gonadotropin release was isolated and its structure was determined by Schally's and Guillemin's groups at the beginning of the 1970s. It was subsequently shown that GnRH is highly conserved among vertebrates. GnRH was assumed the sole hypothalamic neuropeptide that regulates gonadotropin release in vertebrates based on extensive studies of GnRH over the following three decades. However, in 2000, Tsutsui's group isolated and determined the structure of a novel hypothalamic neuropeptide, which inhibits gonadotropin release, in quail, an avian species, and named it gonadotropin-inhibitory hormone (GnIH). Following studies by Tsutsui's group demonstrated that GnIH is highly conserved among vertebrates, from humans to agnathans, and acts as a key neuropeptide inhibiting reproduction. Intensive research on GnIH demonstrated that GnIH inhibits gonadotropin synthesis and release by acting on gonadotropes and GnRH neurons via GPR147 in birds and mammals. Fish GnIH also regulates gonadotropin release according to its reproductive condition, indicating the conserved role of GnIH in the regulation of the hypothalamic-pituitary-gonadal (HPG) axis in vertebrates. Therefore, we can now say that GnRH is not the only hypothalamic neuropeptide controlling vertebrate reproduction. In addition, recent studies by Tsutsui's group demonstrated that GnIH acts in the brain to regulate behaviors, including reproductive behavior. The 18 years of GnIH research with leading laboratories in the world have significantly advanced our knowledge of the neuroendocrine control mechanism of reproductive physiology and behavior as well as interactions of the HPG, hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes. This review describes how GnIH was discovered and GnIH research progressed in this new research era of reproductive neuroendocrinology.

Seasonal regulation of steroidogenic enzyme expression within the green anole lizard (Anolis carolinensis) brain and gonad

Steroid hormones, such as testosterone and estradiol, are necessary for reproductive behavior. Seasonally breeding animals have increased sex steroid hormone levels during the breeding compared to non-breeding season, with increased reproductive behaviors and altered brain morphology in breeding individuals. Similar to other seasonally breeding animals, green anole lizards (Anolis carolinensis) have high sex steroid hormone levels and increased reproductive behaviors in the breeding season. Relatively less is known regarding the regulation of steroidogenesis in reptiles and this experiment examined whether enzymes involved in sex steroid hormone synthesis vary seasonally within the brain and gonads in wild-caught anole lizards. Specifically, we examined mRNA expression of steroidogenic acute regulatory protein (StAR), P450 17α-hydroxylase/C17-20lyase (Cyp17α1), 17 beta-hydroxysteroid dehydrogenase type 3 (17βHSD 3), and aromatase (Cyp19α1). We found that the mRNA for each of these genes was expressed in the lizard brain. Interestingly, Cyp19α1 mRNA expression in the brain was increased during the non-breeding season, potentially revealing a role for aromatase expression in the non-breeding brain. In the anole gonads, StAR mRNA expression levels were increased in both males and females during the breeding season, while the mRNA expression levels of CYP17α1 and 17βHSD 3 are increased when StAR mRNA expression was decreased, suggesting that the enzymes in the steroidogenic pathway are potentially regulated independently of StAR. This work reveals the seasonal regulation of steroidogenesis in the reptilian brain and gonad, although more work is necessary to determine the regulatory mechanisms that control these expression patterns.

An overview of Jatropha curcas meal-induced productive and reproductive toxicity in Japanese quail: Potential mechanisms and heat detoxification

The present study was carried out to investigate the toxic effects of dietary inclusion of raw Jatropha cucas meal [RJM, 3.5%] on productive and reproductive performances of laying Japanese quail and the influence of physical treatment of jatropha meal by heating at [100 ^oc] for 24 or 48 h [JH₂₄ or JH₄₈ respectively] on reducing these effects. The inclusion of RJM in quail diets significantly decreased the egg production, fertility and hatchability percentages and resulted in a high mortality rate. While heat-treated jatropha meal [JH₂₄ or JH₄₈] improved such undesirable effects. The levels of hepatic proteins related to lipid synthesis, cholesterol metabolism and those related to lipid synthesis and transporting to egg yolk were increased in JH₂₄ and JH₄₈ groups than RJM group. Hepatic contents of vitellogenin [VGT-II] and estrogen receptor α [ERα] and circulating estradiol [E2] were improved in JH₄₈ than RJM and JH₂₄ groups however still under the control values. On the other hand, estrogen receptor β [ERβ] were restored to normal control value in both JH₂₄ and JH₄₈ groups. Histopathological investigation revealed that RJM produced various alterations in the histoarchitecture of liver, ovary and oviducts but these alterations were reduced in both JH₂₄ and JH₄₈ groups. From the obtained data we concluded that heating of jatropha meal for 24 h improved its nutritive value and increasing the time of heating is preferable for reduction of the most of toxic impacts indicating that heat treatment can convert toxic jatropha meal to an alternative protein source for livestock feed in a cheap and clean way without combining any other types of treatments.

Dual action of neuro-estrogens in the regulation of male sexual behavior

Estrogens derived from brain testosterone aromatization (neuro-estrogens) are critical for the activation of male sexual behavior. Their effects on this behavior are typically associated with long-term changes in circulating levels of testosterone and the transcriptional activity of their liganded nuclear receptors. According to this view, neuro-estrogens would prime the neural circuits controlling the long-term expression of behavior, which would then be acutely regulated by neurotransmitter systems conveying information from the social environment. In parallel, neuro-estrogens are also able to produce much faster effects than previously anticipated. Our recent investigations in Japanese quail revealed an interesting dichotomy in the regulation of male sexual behavior by membrane- and nuclear-initiated estrogen signaling providing respectively an acute modulation of sexual motivation and a long-term control of the capacity to display the copulatory sequence. In parallel, a similar dichotomy applies to the regulation of brain aromatase whose expression depends on the transcriptional activity of testosterone metabolites while its enzymatic activity is rapidly regulated in a region- and context-dependent manner. Recent evidences suggest that rapid changes in sexual motivation result from rapid changes in local estrogen production. Together, these data support the idea that the acute regulation of some aspects of male sexual behavior depends not only on classical neurotransmitter systems, but also on rapid and spatially restricted changes in local estrogen availability. The existing literature suggests that this acute regulation by neuro-estrogens of the motivational aspects of behavior could be generalized to other systems such as singing behavior in songbirds.

Neuroendocrine correlates of sex-role reversal in barred buttonquails

Sex differences in brain structure and behaviour are well documented among vertebrates. An excellent model exploring the neural mechanisms of sex differences in behaviour is represented by sex-role-reversed species. In the majority of bird species, males compete over access to mates and resources more strongly than do females. It is thought that the responsible brain regions are therefore more developed in males than in females. Because these behaviours and brain regions are activated by androgens, males usually have increased testosterone levels during breeding. Therefore, in species with sex-role reversal, certain areas of the female brain should be more developed or steroid hormone profiles should be sexually reversed. Here, I studied circulating hormone levels and gene expression of steroid hormone receptors and aromatase in a captive population of barred buttonquails (Turnix suscitator). While females performed courtship and agonistic behaviours, there was no evidence for sexually reversed hormone profiles. However, I found female-biased sex differences in gene expression of androgen receptors in several hypothalamic and limbic brain regions that were already in place at hatching. Such sex differences are not known from non-sex-role-reversed species. These data suggest that increased neural sensitivity to androgens could be involved in the mechanisms mediating sex-role-reversed behaviours.

Steroid metabolism in the brain: From bird watching to molecular biology, a personal journey

Since Arnold Adolph Berthold established in 1849 the critical role of the testes in the activation of male sexual behavior, intensive research has identified many sophisticated neurochemical and molecular mechanisms mediating this action. Studies in Japanese quail demonstrated the critical role of testosterone action and of testosterone aromatization in the sexually dimorphic medial preoptic nucleus in the activation of male copulatory behavior. The development of an immunohistochemical visualization of brain aromatase in quail then allowed further refinement in the localization of the sites of neuroestrogens production. Testosterone aromatization is required for the activation of both appetitive and consummatory aspects of male sexual behavior. Brain aromatase activity is modulated by steroid-induced changes in the transcription of the corresponding gene but also more rapidly by phosphorylation processes. Sexual interactions with a female also rapidly regulate brain aromatase activity in an anatomically specific manner presumably via the release and action of endogenous glutamate. These rapid changes in estrogen production modulate sexual behavior and in particular its motivational component with latencies ranging between 15 and 30min. Brain estrogens seem to act in a manner akin to a neurotransmitter or at least a neuromodulator. More recently, assays of brain estradiol concentrations in micropunched samples or in dialysis samples obtained from behaviorally active males suggested that aromatase activity measured ex vivo might not be an accurate proxy to the rapid changes in local neuroestrogens production and concentrations. Studies of brain testosterone metabolism are thus not over and will keep scientists busy for a little longer. Elsevier SBN Keynote Address, Montreal.

Seasonal changes and sexual dimorphism in gene expression of StAR protein, steroidogenic enzymes and sex hormone receptors in the frog brain

The brain of amphibians contains all the key enzymes of steroidogenesis and has a high steroidogenic activity. In seasonally-breeding amphibian species brain steroid levels fluctuate synchronously with the reproductive cycle. Here we report a study of gene expression of StAR protein, key steroidogenic enzymes and sex hormone receptors in the telencephalon (T) and diencephalon-mesencephalon (D-M) of male and female reproductive and post-reproductive Pelophylax esculentus, a seasonally breeding anuran amphibian. Significant differences in gene expression were observed between (a) the reproductive and post-reproductive phase, (b) the two brain regions and (c) male and female frogs. During the reproductive phase, star gene expression increased in the male (both T and D-M) but not in the female brain. Seasonal fluctuations in expression levels of hsd3b1, hsd17b1, srd5a1 and cyp19a1 genes for neurosteroidogenic enzymes occurred in D-M region of both sexes, with the higher levels in reproductive period. Moreover, the D-M region generally showed higher levels of gene expression than the T region in both sexes. Gene expression was higher in females than males for most genes, suggesting higher neurosteroid production in female brain. Seasonal and sex-linked changes were also observed in gene expression for androgen (ar) and estrogen (esr1, esr2) receptors, with the males showing the highest ar levels in reproductive phase and the highest esr1 and esr2 levels in post-reproductive phase; in contrast, females showed the maximum expression for all three genes in reproductive phase. The results are the first evidence for seasonal changes and sexual dimorphism of gene expression of the neurosteroidogenic pathway in amphibians.

Neuroendocrine disruption of organizational and activational hormone programming in poikilothermic vertebrates

In vertebrates, sexual differentiation of the reproductive system and brain is tightly orchestrated by organizational and activational effects of endogenous hormones. In mammals and birds, the organizational period is typified by a surge of sex hormones during differentiation of specific neural circuits; whereas activational effects are dependent upon later increases in these same hormones at sexual maturation. Depending on the reproductive organ or brain region, initial programming events may be modulated by androgens or require conversion of androgens to estrogens. The prevailing notion based upon findings in mammalian models is that male brain is sculpted to undergo masculinization and defeminization. In absence of these responses, the female brain develops. While timing of organizational and activational events vary across taxa, there are shared features. Further, exposure of different animal models to environmental chemicals such as xenoestrogens such as bisphenol A-BPA and ethinylestradiol-EE2, gestagens, and thyroid hormone disruptors, broadly classified as neuroendocrine disrupting chemicals (NED), during these critical periods may result in similar alterations in brain structure, function, and consequently, behaviors. Organizational effects of neuroendocrine systems in mammals and birds appear to be permanent, whereas teleost fish neuroendocrine systems exhibit plasticity. While there are fewer NED studies in amphibians and reptiles, data suggest that NED disrupt normal organizational-activational effects of endogenous hormones, although it remains to be determined if these disturbances are reversible. The aim of this review is to examine how various environmental chemicals may interrupt normal organizational and activational events in poikilothermic vertebrates. By altering such processes, these chemicals may affect reproductive health of an animal and result in compromised populations and ecosystem-level effects.

Sexually Diergic Trophic Effects of Estradiol Exposure on Developing Bovine Cerebellar Granule Cells

In the mammalian brain, the differentiation of neural cells and the developmental organization of the underlying circuitry are influenced by steroid hormones. The estrogen 17-β estradiol (E2) is one of the most potent regulators of neural growth during prenatal life, synthetized locally from steroid precursors including prenatal testicular testosterone. Estradiol promotes brain differentiation counting sexually dimorphic neural circuits by binding to the estrogen receptors, ER-α and ER-β. The cerebellum has been described as a site of estrogen action and a potentially sexually dimorphic area. The goal of this study was to analyze the capacity of E2 to affect the growth of male and female fetal bovine cerebellar granule. We performed primary cultures of fetal cerebellar granules, and verified the mRNA expression of the ER-α and ER-β in both sexes. Moreover, the distribution of ERs in the male and female cerebellar granules of the second fetal stage was characterized by immunohistochemistry. We measured morphological parameters in presence (or absence) of estradiol administration, focusing on the variations of the dendritic branching pattern of granule neurons. By using the nonparametric combination and permutation testing approach, we proposed a sophisticated multivariate statistical analysis to demonstrate that E2 induces multifarious and dimorphic changes in the granule cells. E2 exerts trophic effects in both female and male granules and this effect is stronger in female. Male granules treated with E2 became similar to female control granule. Bos taurus species has a long gestation and a large brain that offers an interesting alternative in comparative neuroscience.

Non-ovarian aromatization is required to activate female sexual motivation in testosterone-treated ovariectomized quail

Although aromatase is expressed in both male and female brains, its functional significance in females remains poorly understood. In female quail, sexual receptivity is activated by estrogens. However it is not known whether sexual motivation is similarly estrogen-dependent and whether estrogens locally produced in the brain contribute to these behavioral responses. Four main experiments were designed to address these questions. In Experiment 1 chronic treatment of females with the anti-estrogen tamoxifen decreased their receptivity, confirming that this response is under the control of estrogens. In Experiment 2 chronic treatment with tamoxifen significantly decreased sexual motivation as treated females no longer approached a sexual partner. In Experiment 3 (a) ovariectomy (OVX) induced a significant decrease of time spent near the male and a significantly decreased receptivity compared to gonadally intact females, (b) treatment with testosterone (OVX+T) partially restored these responses and (c) this effect of T was prevented when estradiol synthesis was inhibited by the potent aromatase inhibitor Vorozole (OVX+T+VOR). Serum estradiol concentration was significantly higher in OVX+T than in OVX or OVX+T+VOR females. Together these data demonstrate that treatment of OVX females with T increases sexual motivation and that these effects are mediated at least in part by non-gonadal aromatization of the androgen. Finally, assays of aromatase activity on brain and peripheral tissues (Experiment 4) strongly suggest that brain aromatization contributes to behavioral effects observed here following T treatment but alternative sources of estrogens (e.g. liver) should also be considered.

7α-Hydroxypregnenolone regulates diurnal changes in sexual behavior of male quail

In the Japanese quail, 7α-hydroxypregnenolone, a previously undescribed avian neurosteroid, is actively produced in the brain. 7α-Hydroxypregnenolone acts as a novel neuronal activator to stimulate locomotor activity of quail. Therefore, in this study, we determined whether 7α-hydroxypregnenolone changes the expression of sexual behavior in Japanese quail. We first measured diurnal changes in sexual behavior of male quail exposed to a long-day photoperiod. We found that sexual behavior of male quail was high in the morning when endogenous 7α-hydroxypregnenolone level is high. Subsequently, we centrally administered 7α-hydroxypregnenolone in the evening when endogenous 7α-hydroxypregnenolone level is low. In the 30 min after intracerebroventricular (ICV) injection, 7α-hydroxypregnenolone dose dependently increased the frequency of sexual behavior of male quail. However, 7β-hydroxypregnenolone, a stereoisomer of 7α-hydroxypregnenolone, did not effect on the frequency of sexual behavior of male quail. In addition, to confirm the action of 7α-hydroxypregnenolone on sexual behavior, male birds received an ICV injection of ketoconazole, an inhibitor of cytochrome P450s, and behavioral experiments were performed in the morning. Ketoconazole significantly decreased the frequency of sexual behavior of male quail, whereas administration of 7α-hydroxypregnenolone to ketoconazole-treated males increased the frequency of their sexual behavior. These results indicate that 7α-hydroxypregnenolone regulates diurnal changes in sexual behavior of male quail.

How to contribute to the progress of neuroendocrinology: New insights from discovering novel neuropeptides and neurosteroids regulating pituitary and brain functions

Obtaining new insights by discovering novel neuropeptides and neurosteroids regulating pituitary and brain functions is essential for the progress of neuroendocrinology. At the beginning of 1970s, gonadotropin-releasing hormone (GnRH) was discovered in mammals. Since then, it was generally accepted that GnRH is the only hypothalamic neuropeptide regulating gonadotropin release in vertebrates. In 2000, however, gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that actively inhibits gonadotropin release, was discovered in quail. The follow-up studies demonstrated that GnIH acts as a new key player for regulation of reproduction across vertebrates. It now appears that GnIH acts on the pituitary and the brain to serve a number of behavioral and physiological functions. On the other hand, a new concept has been established that the brain synthesizes steroids, called neurosteroids. The formation of neurosteroids in the brain was originally demonstrated in mammals and subsequently in other vertebrates. Recently, 7α-hydroxypregnenolone was discovered as a novel bioactive neurosteroid inducing locomotor behavior of vertebrates, indicating that neurosteroidogenesis in the brain is still incompletely elucidated in vertebrates. At the beginning of 2010s, it was further found that the pineal gland actively produces neurosteroids. Pineal neurosteroids act on the brain to regulate locomotor rhythms and neuronal survival. Furthermore, the interaction of neuropeptides and neurosteroids is becoming clear. GnIH decreases aggressive behavior by regulating neuroestrogen synthesis in the brain. This review summarizes these new insights by discovering novel neuropeptides and neurosteroids in the field of neuroendocrinology.

Molecular, cellular, morphological, physiological and behavioral aspects of gonadotropin-inhibitory hormone

Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that was isolated from the brains of Japanese quail in 2000, which inhibited luteinizing hormone release from the anterior pituitary gland. Here, we summarize the following fifteen years of researches that investigated on the mechanism of GnIH actions at molecular, cellular, morphological, physiological, and behavioral levels. The unique molecular structure of GnIH peptide is in its LPXRFamide (X=L or Q) motif at its C-terminal. The primary receptor for GnIH is GPR147. The cell signaling pathway triggered by GnIH is initiated by inhibiting adenylate cyclase and decreasing cAMP production in the target cell. GnIH neurons regulate not only gonadotropin synthesis and release in the pituitary, but also regulate various neurons in the brain, such as GnRH1, GnRH2, dopamine, POMC, NPY, orexin, MCH, CRH, oxytocin, and kisspeptin neurons. GnIH and GPR147 are also expressed in gonads and they may regulate steroidogenesis and germ cell maturation in an autocrine/paracrine manner. GnIH regulates reproductive development and activity. In female mammals, GnIH may regulate estrous or menstrual cycle. GnIH is also involved in the regulation of seasonal reproduction, but GnIH may finely tune reproductive activities in the breeding seasons. It is involved in stress responses not only in the brain but also in gonads. GnIH may inhibit male socio-sexual behavior by stimulating the activity of cytochrome P450 aromatase in the brain and stimulates feeding behavior by modulating the activities of hypothalamic and central amygdala neurons.

Hypothalamic inhibition of socio-sexual behaviour by increasing neuroestrogen synthesis

Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotropin secretion and socio-sexual behaviours. Oestrogen (neuroestrogen) synthesized in the brain from androgen by aromatase regulates male socio-sexual behaviours. Here we show that GnIH directly activates aromatase and increases neuroestrogen synthesis in the preoptic area (POA) and inhibits socio-sexual behaviours of male quail. Aromatase activity and neuroestrogen concentration in the POA are low in the morning when the birds are active, but neuroestrogen synthesis gradually increases until the evening when the birds become inactive. Centrally administered GnIH in the morning increases neuroestrogen synthesis in the POA and decreases socio-sexual behaviours. Centrally administered 17β-oestradiol at higher doses also inhibits socio-sexual behaviours in the morning. These results suggest that GnIH inhibits male socio-sexual behaviours by increasing neuroestrogen synthesis beyond its optimum concentration for the expression of socio-sexual behaviours. This is the first demonstration of any hypothalamic neuropeptide that directly regulates neuroestrogen synthesis.

Expression of the cyp19a1 gene in the adult brain of Xenopus is neuronal and not sexually dimorphic

The last step of oestrogen biosynthesis is catalyzed by the enzyme aromatase, the product of the cyp19a1 gene. In vertebrates, cyp19a1 is expressed in the brain resulting in a local oestrogen production that seems important not only for the control of reproduction-related circuits and sexual behaviour, but also for the regulation of neural development, synaptic plasticity and cell survival. In adult amphibians, the precise sites of expression of cyp19a1 in the brain have not been investigated which prevents proper understanding of its potential physiological functions. The present study aimed at examining the precise neuroanatomical distribution of cyp19a1 transcripts in adult brains of both male and female Xenopus. We found that cyp19a1 expression is highly regionalized in the brains of both sexes. The highest expression was found in the anterior part of the preoptic area and in the caudal hypothalamus, but significant levels of cyp19a1 transcripts were also found in the supraoptic paraventricular and suprachiasmatic areas, and in brain regions corresponding to the septum, bed nucleus of the stria terminalis and amygdala. Importantly, no obvious difference between male and female Xenopus was detected at the level of cyp19a1 transcripts. Additionally, in the brain of adult Xenopus, cyp19a1 transcripts were detected in neurons, and not in glial cells. These data and those available in other vertebrates on cyp19a1/aromatase expression suggest that, with the intriguing exception of teleost fishes, cyp19a1 was under strong evolutionary conservation with respect to its sites of expression and the nature of the cells in which it is expressed.

Rapid Effects of Estradiol on Aggression in Birds and Mice: The Fast and the Furious

Across invertebrates and vertebrates, steroids are potent signaling molecules that affect nearly every cell in the organism, including cells of the nervous system. Historically, researchers have focused on the genomic (or "nuclear-initiated") effects of steroids. However, all classes of steroids also have rapid non-genomic (or "membrane-initiated") effects, although there is far less basic knowledge of these non-genomic effects. In particular, steroids synthesized in the brain ("neurosteroids") have genomic and non-genomic effects on behavior. Here, we review evidence that estradiol has rapid effects on aggression, an important social behavior, and on intracellular signaling cascades in relevant regions of the brain. In particular, we focus on studies of song sparrows (Melospiza melodia) and Peromyscus mice, in which estradiol has rapid behavioral effects under short photoperiods only. Furthermore, in captive Peromyscus, estrogenic compounds (THF-diols) in corncob bedding profoundly alter the rapid effects of estradiol. Environmental factors in the laboratory, such as photoperiod, diet, and bedding, are critical variables to consider in experimental design. These studies are consistent with the hypothesis that locally-produced steroids are more likely than systemic steroids to act via non-genomic mechanisms. Furthermore, these studies illustrate the dynamic balance between genomic and non-genomic signaling for estradiol, which is likely to be relevant for other steroids, behaviors, and species.

Contribution of GnIH Research to the Progress of Reproductive Neuroendocrinology

Since the discovery of gonadotropin-releasing hormone (GnRH) in mammals at the beginning of the 1970s, it was generally accepted that GnRH is the only hypothalamic neuropeptide regulating gonadotropin release in mammals and other vertebrates. In 2000, however, gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that actively inhibits gonadotropin release, was discovered in quail. Numerous studies over the past decade and a half have demonstrated that GnIH serves as a key player regulating reproduction across vertebrates, acting on the brain and pituitary to modulate reproductive physiology and behavior. In the latter case, recent evidence indicates that GnIH can regulate reproductive behavior through changes in neurosteroid, such as neuroestrogen, biosynthesis in the brain. This review summarizes the discovery of GnIH, and the contributions to GnIH research focused on its mode of action, regulation of biosynthesis, and how these findings advance our understanding of reproductive neuroendocrinology.

Review: neuroestrogen regulation of socio-sexual behavior of males

It is thought that estrogen (neuroestrogen) synthesized by the action of aromatase in the brain from testosterone activates male socio-sexual behaviors, such as aggression and sexual behavior in birds. We recently found that gonadotropin-inhibitory hormone (GnIH), a hypothalamic neuropeptide, inhibits socio-sexual behaviors of male quail by directly activating aromatase and increasing neuroestrogen synthesis in the preoptic area (POA). The POA is thought to be the most critical site of aromatization and neuroestrogen action for the regulation of socio-sexual behavior of male birds. We concluded that GnIH inhibits socio-sexual behaviors of male quail by increasing neuroestrogen concentration beyond its optimal concentration in the brain for expression of socio-sexual behavior. On the other hand, it has been reported that dopamine and glutamate, which stimulate male socio-sexual behavior in birds and mammals, inhibit the activity of aromatase in the POA. Multiple studies also report that the activity of aromatase or neuroestrogen is negatively correlated with changes in male socio-sexual behavior in fish, birds, and mammals including humans. Here, we review previous studies that investigated the role of neuroestrogen in the regulation of male socio-sexual behavior and reconsider the hypothesis that neuroestrogen activates male socio-sexual behavior in vertebrates. It is considered that basal concentration of neuroestrogen is required for the maintenance of male socio-sexual behavior but higher concentration of neuroestrogen may inhibit male socio-sexual behavior.

Gonadotropin-inhibitory hormone inhibits aggressive behavior of male quail by increasing neuroestrogen synthesis in the brain beyond its optimum concentration

The action of testosterone on male socio-sexual behaviors, such as aggressive and sexual behaviors, requires its aromatization into estrogen (neuroestrogen) in the brain. Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotropin secretion from the pituitary. On the other hand, wide distribution of GnIH-immunoreactive (ir) neuronal fibers in the brain suggested their roles in the regulation of behavior. Our recent studies have shown that GnIH indeed inhibits aggressive and sexual behaviors. Accordingly, we further investigated the effect of GnIH on aromatase activity and estrogen synthesis in the brain. Abundant GnIH-ir neuronal fibers were observed in the vicinity of aromatase-ir cells in the brain, such as in the preoptic area (POA) that is thought to be the most critical site of aromatization and neuroestrogen action for the regulation of socio-sexual behavior. GnIH receptor (GPR147) mRNA was also expressed in aromatase-ir cells in the POA. GnIH stimulated the activity of aromatase and increased neuroestrogen synthesis in the POA through GPR147. The increase in neuroestrogen concentration in the POA was associated with a significant decrease in aggressive behavior. Finally, centrally administered 17β-estradiol at higher doses inhibited aggressive behavior. These findings indicated that GnIH inhibits aggressive behavior by directly activating aromatase and increasing neuroestrogen synthesis in the brain beyond its optimum concentration for the expression of aggressive behavior. This review highlights recent findings of the role of GnIH in the regulation of neuroestrogen synthesis and its possible function in the regulation of socio-sexual behaviors.

Cyp19a1 (aromatase) expression in the Xenopus brain at different developmental stages

Cytochrome P450 aromatase (P450arom; aromatase) is a microsomal enzyme involved in the production of endogeneous sex steroids by converting testosterone into oestradiol. Aromatase is the product of the cyp19a1 gene and plays a crucial role in the sexual differentiation of the brain and in the regulation of reproductive functions. In the brain of mammals and birds, expression of cyp19a1 has been demonstrated in neuronal populations of the telencephalon and diencephalon. By contrast, a wealth of evidence established that, in teleost fishes, aromatase expression in the brain is restricted to radial glial cells. The present study investigated the precise neuroanatomical distribution of cyp19a1 mRNA during brain development in Xenopus laevis (late embryonic to juvenile stages). For this purpose, we used in situ hybridisation alone or combined with the detection of a proliferative (proliferating cell nuclear antigen), glial (brain lipid binding protein, Vimentin) or neuronal (acetylated tubulin; HuC/D; NeuroβTubulin) markers. We provide evidence that cyp19a1 expression in the brain is initiated from the very early larval stage and remains strongly detected until the juvenile and adult stages. At all stages analysed, we found the highest expression of cyp19a1 in the preoptic area and the hypothalamus compared to the rest of the brain. In these two brain regions, cyp19a1-positive cells were never detected in the ventricular layers. Indeed, no co-labelling could be observed with radial glial (brain lipid binding protein, Vimentin) or dividing progenitors (proliferating cell nuclear antigen) markers. By contrast, cyp19a1-positive cells perfectly matched with the distribution of post-mitotic neurones as shown by the use of specific markers (HuC/D, acetylated tubulin and NeuroβTubulin). These data suggest that, similar to that found in other tetrapods, aromatase in the brain of amphibians is found in post-mitotic neurones and not in radial glia as reported in teleosts.

Relationships between rapid changes in local aromatase activity and estradiol concentrations in male and female quail brain

Estradiol-17β (E2) synthesized in the brain plays a critical role in the activation of sexual behavior in many vertebrate species. Because E2 concentrations depend on aromatization of testosterone, changes in aromatase enzymatic activity (AA) are often utilized as a proxy to describe E2 concentrations. Utilizing two types of stimuli (sexual interactions and acute restraint stress) that have been demonstrated to reliably alter AA within minutes in opposite directions (sexual interactions=decrease, stress=increase), we tested in Japanese quail whether rapid changes in AA are paralleled by changes in E2 concentrations in discrete brain areas. In males, E2 in the pooled medial preoptic nucleus/medial portion of the bed nucleus of the stria terminalis (POM/BST) positively correlated with AA following sexual interactions. However, following acute stress, E2 decreased significantly (approximately 2-fold) in the male POM/BST despite a significant increase in AA. In females, AA positively correlated with E2 in both the POM/BST and mediobasal hypothalamus supporting a role for local, as opposed to ovarian, production regulating brain E2 concentrations. In addition, correlations of individual E2 in POM/BST and measurements of female sexual behavior suggested a role for local E2 synthesis in female receptivity. These data demonstrate that local E2 in the male brain changes in response to stimuli on a time course suggestive of potential non-genomic effects on brain and behavior. Overall, this study highlights the complex mechanisms regulating local E2 concentrations including rapid stimulus-driven changes in production and stress-induced changes in catabolism.

Rapid control of reproductive behaviour by locally synthesised oestrogens: focus on aromatase

Oestrogens activate nucleus- and membrane-initiated signalling. Nucleus-initiated events control a wide array of physiological and behavioural responses. These effects generally take place within relatively long periods of time (several hours to days). By contrast, membrane-initiated signalling affects a multitude of cellular functions in a much shorter timeframe (seconds to minutes). However, much less is known about their functional significance. Furthermore, the origin of the oestrogens able to trigger these acute effects is rarely examined. Finally, these two distinct types of oestrogenic actions have often been studied independently such that we do not exactly know how they cooperate to control the same response. The present review presents a synthesis of recent work carried out in our laboratory that aimed to address these issues in the context of the study of male sexual behaviour in Japanese quail, which is a considered as a suitable species for tackling these issues. The first section presents data indicating that 17β-oestradiol, or its membrane impermeable analogues, acutely enhances measures of male sexual motivation but does not affect copulatory behaviour. These effects depend on the activation of membrane-initiated events and local oestrogen production. The second part of this review discusses the regulation of brain oestrogen synthesis through post-translational modifications of the enzyme aromatase. Initially discovered in vitro, these rapid and reversible enzymatic modulations occur in vivo following variations in the social and environment context and therefore provide a mechanism of acute regulation of local oestrogen provision with a spatial and time resolution compatible with the rapid effects observed on male sexual behaviour. Finally, we discuss how these distinct modes of oestrogenic action (membrane- versus nucleus-initiated) acting in different time frames (short- versus long-term) interact to control different components (motivation versus performance) of the same behavioural response and improve reproductive fitness.

Vasotocin mRNA expression is sensitive to testosterone and oestradiol in the bed nucleus of the stria terminalis in female Japanese quail

Vasotocin-producing parvocellular neurones in the medial part of the bed nucleus of the stria terminalis (BSTM) of many species of birds and mammals show sexual dimorphism and great plasticity in response to hormonal and environmental stimuli. In the BSTM of Japanese quail, vasotocin-immunoreactive neurones are visible and sensitive to testosterone exclusively in males. In males, gonadectomy decreases and testosterone restores vasotocin-immunoreactive cells and fibres by acting on vasotocin mRNA transcription. The insensitivity of female vasotocin-immunoreactive neurones to the activating effects of testosterone is the result of organisational effects of early exposure to oestradiol. Female quail also show vasotocin mRNA-expressing neurones in the BSTM, although it is not known whether the insensitivity of the vasotocinergic neurones to testosterone originates at the level of vasotocin gene transcription in this sex. Therefore, initially, the present study analysed the effects of acute treatment with testosterone on vasotocin mRNA expression in the BSTM of gonadectomised male and female quail using in situ hybridisation. Gonadectomy decreased (and a single injection of testosterone increased) the number of vasotocin mRNA-expressing neurones and intensity of the vasotocin mRNA hybridisation signal similarly in both sexes. Notably, testosterone increased vasotocin mRNA expression in ovariectomised females over that shown by intact quail. However, this treatment had no effect on vasotocin immunoreactivity. A second experiment analysed the effects of testosterone metabolites, oestradiol and 5α-dihydrotestosterone, on vasotocin mRNA expression in female quail. Oestradiol (but not 5α-dihydrotestosterone) fully mimicked the effects of testosterone on the number of vasotocin mRNA-expressing neurones and the intensity of the vasotocin mRNA hybridisation signal. Taken together, these results show, for the first time, that gonadal steroids strongly activate vasotocin mRNA expression in the BSTM of female quail.

Neurochemical control of rapid stress-induced changes in brain aromatase activity

In the male brain, the medial preoptic nucleus (POM) is known to be a critical relay for the activation of sexual behaviour, with the aromatisation of testosterone into 17β-oestradiol (E2 ) playing a key role. Acute stress has been shown to differentially modulate the aromatase enzyme in this and other brain nuclei in a sex-specific manner. In POM specifically, stress induces increases in aromatase activity (AA) that are both rapid and reversible. How the physiological processes initiated during an acute stress response mediate sex- and nuclei- specific changes in AA and which stress response hormones are involved remains to be determined. By examining the relative effects of corticosterone (CORT), arginine vasotocin (AVT, the avian homologue to arginine vasopressin) and corticotrophin-releasing factor (CRF), the present study aimed to define the hormone profile regulating stress-induced increases in AA in the POM. We found that CORT, AVT and CRF all appear to play some role in these changes in the male brain. In addition, these effects occur in a targeted manner, such that modulation of the enzyme by these hormones only occurs in the POM rather than in all aromatase-expressing nuclei. Similarly, in the female brain, the experimental effects were restricted to the POM but only CRF was capable of inducing the stress-like increases in AA. These data further demonstrate the high degree of specificity (nuclei-, sex- and hormone-specific effects) in this system, highlighting the complexity of the stress-aromatase link and suggesting modes through which the nongenomic modulation of this enzyme can result in targeted, rapid changes in local oestrogen concentrations.

D-Aspartic acid implication in the modulation of frog brain sex steroid levels

There is evidence that D-aspartate (D-Asp) modulates sex hormone levels in frog testis by regulating the activity of P450 aromatase (P450 aro), the key enzyme which converts Testosterone (T) in 17ß-Estradiol (E2). Here we report, for the first time, that there is a direct correlation among brain levels of D-Asp, P450 aro, E2 and Estradiol Receptor (ERα) in the male frogs during the reproductive as well as the post-reproductive phases of the breeding cycle, with highest levels being observed in the post-reproductive period. D-Asp i.p. administration to frogs ready for reproduction, induced an increase of brain P450 aro protein expression with concomitant enhancement of both E2 levels and ERα expression; at the same time, brain T levels and Androgen receptor expression decreased. In contrast, in the post-reproductive frogs, D-Asp treatment did not modify any of these parameters. Taken together, these results imply that the regulation of P450 aro expression by D-Asp could be an important step in the control of E2 levels in the frog brain.