Estradiol-Dependent and -Independent Stimulation of Kiss1 Expression in the Amygdala, BNST, and Lateral Septum of Mice

Sexually dimorphic distribution of Kiss1 neurons in the bed nucleus of the stria terminalis

Kiss1 neurons play a crucial role in reproductive function and are found in distinct brain regions, including the bed nucleus of the stria terminalis (BNST). However, the sexual dimorphism of Kiss1 neurons in the BNST and their projections has not been fully characterized. This study examined the distribution and projections of Kiss1 neurons in the anterior (aBNST) and principal (prBNST) regions of the BNST in male and female Kiss1-Cre and Kiss1-Cre; tdTomatoloxP/+ mice. Neuroanatomical analysis and tracing experiments were conducted to quantify Kiss1 neurons and map their projections. Males had approximately a threefold higher number of Kiss1 neurons in the prBNST than females, while no significant sex difference was observed in the aBNST. Viral tracing experiments revealed sexually dimorphic projections of Kiss1adBNST neurons, with females displaying more diverse projections to various brain regions involved in reproduction and social behaviors. Kiss1prBNST neurons project exclusively to the zona incerta and adBNST in both sexes, while females exhibited additional projections to the RP3V and PVH. The sexually dimorphic distribution and projections of Kiss1BNST neurons suggest their potential role in modulating sex-specific behaviors and neuroendocrine functions. This neuroanatomical sexual dimorphism may contribute to sex differences in social and reproductive behaviors associated with BNST function, providing new insights into the neural basis of sex-specific behaviors and reproductive regulation.

Investigating glymphatic function and bed nucleus of the stria terminalis-based functional connectivity in Parkinson's disease with and without depression

Glymphatic activity and the bed nucleus of the stria terminalis (BNST) have been implicated in the pathogenesis of Parkinson's disease (PD) with depression (PDD). This study aimed to investigate glymphatic function and BNST-based functional connectivity (FC) and potential biomarkers in PDD. The diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) index combined with BNST-based FC and support vector machine were applied to 24 PDD, 24 PD with non-depression (PDND), and 25 healthy controls. We found that (1) the DTI-ALPS indices (p < 0.001), the right BNST-based FC values (p < 0.001, FWE small volume correction) were significantly different among three groups; (2) the FC features in the right mPFC (mPFC_R), right MTG (MTG_R), and right ITG (ITG_R) can distinguish PDD from PDND; (3) the right BNST-based FC values, DTI-ALPS indices, and HAMD scores were correlated with each other (r = -0.620, p = 0.004; r = 0.651, p = 0.002; r = -0.53, p = 0.016). Impaired glymphatic function and altered BNST-based FC values are strongly associated with PD, and brain regions with differences in the right BNST-based FC values may serve as potential biomarkers for classifying clinical subtypes of PD. These findings provide new insights into the pathogenesis of depression in PD. This study protocol was registered on the Chinese Clinical Trial Registry (ChiCTR2000038411, September 22, 2020, https://www.chictr.org.cn/showproj.html?proj=56715 ).

Comprehensive chemoanatomical mapping, and the gonadal regulation, of seven kisspeptin neuronal populations in the mouse brain

Kisspeptinergic signaling is well-established as crucial for the regulation of reproduction, but its potential broader role in brain function is less understood. This study investigates the distribution and chemotyping of kisspeptin-expressing neurons within the mouse brain. RNAscope single, dual, and multiplex in situ hybridization methods were used to assess kisspeptin mRNA (Kiss1) expression and its co-expression with other neuropeptides, excitatory and inhibitory neurotransmitter markers, and sex steroid receptors in wild-type intact and gonadectomized young adult mice. Seven distinct kisspeptin neuronal chemotypes were characterized, including two novel kisspeptin-expressing groups described for the first time, that is, the Kiss1 population in the ventral premammillary nucleus and the nucleus of the solitary tract. Kiss1 mRNA was also observed to localize in both somatic and dendritic compartments of hypothalamic neurons. High androgen receptor expression and changes in medial amygdala and septo-hypothalamic Kiss1 expression following GDX in males, but not in females, suggest a role for androgen receptors in regulating kisspeptin signaling. This study provides a detailed chemoanatomical map of kisspeptin-expressing neurons, highlighting their potential functional diversity. The discovery of a new kisspeptin-expressing group and gonadectomy-induced changes in Kiss1 expression patterns suggest broader roles for kisspeptin in brain functions beyond those of reproduction.

Anatomic distribution of kisspeptin neurons in the adult sheep amygdala: Associations with sex, estrogen receptor alpha, androgen receptor, and sexual partner preference

Kisspeptin neurons are primarily known for regulating reproductive function by stimulating hormone release that controls puberty and fertility. While typically associated with the hypothalamus, recent research suggests their presence in other brain regions, including the amygdala. The amygdala, crucial for emotional processing and social behaviors, consists of various nuclei. However, the specific distribution and potential functional implications of kisspeptin neurons within this region remain unclear. Understanding kisspeptin neuron distribution in the sheep amygdala could provide insights into their roles in modulating reproductive functions, emotional, and social behaviors in a species closely related to humans. This study employed immunohistochemistry and RNAscope™ fluorescent in situ hybridization to map the distribution of kisspeptin fibers and cells in the amygdala of intact adult male and luteal-phase female sheep. The research also investigated the co-expression of Kiss1 with estrogen receptor-α (ESR1) and androgen receptor (AR) mRNA, as well as the presence of kisspeptin receptor (Kiss1r) mRNA-containing cells. Kisspeptin immunoreactive fibers were most dense in the medial amygdala, while Kiss1 mRNA-containing cells were abundant in the medial, cortical, and basal nuclei. Extensive co-expression of Kiss1 with ESR1 and AR mRNA was observed. In the posterior medial nucleus, 80% of kisspeptin neurons co-expressed ESR1, and 40% co-expressed AR. Kiss1r mRNA-containing cells were found in the medial, cortical, and basal nuclei and co-localized within cells expressing Kiss1 mRNA. No differences in kisspeptin cell numbers were found between rams and ewes or between rams with different sexual partner preferences. This study provides a foundational map of the kisspeptin system in the sheep amygdala, offering insights into its potential roles in reproductive, emotional, and social behaviors. The extensive co-expression of Kiss1 mRNA with ESR1 and AR mRNA suggests possible regulation by sex steroids, while the presence of Kiss1r mRNA-containing cells indicates potential autocrine or paracrine signaling. These findings contribute to our understanding of kisspeptin neurons' distribution and potential functions beyond the hypothalamus, particularly in the amygdala.

Estrogen-Regulated Lateral Septal Kisspeptin Neurons Abundantly Project to GnRH Neurons and the Hypothalamic Supramammillary Nucleus

While hypothalamic kisspeptin (KP) neurons play well-established roles in the estrogen-dependent regulation of reproduction, little is known about extrahypothalamic KP-producing (KPLS) neurons of the lateral septum. As established previously, Kiss1 expression in this region is low and regulated by estrogen receptor- and GABAB receptor-dependent mechanisms. Our present experiments on Kiss1-Cre/ZsGreen knock-in mice revealed that transgene expression in the LS begins at Postnatal Day (P)33-36 in females and P40-45 in males and is stimulated by estrogen receptor signaling. Fluorescent cell numbers continue to increase in adulthood and are higher in females. Viral tracing uncovered that the bulk of KPLS fibers joins the medial forebrain bundle and terminates in the hypothalamic supramammillary nucleus. Smaller subsets innervate the medial amygdala or project to other limbic structures. One-quarter of gonadotropin-releasing hormone (GnRH)-immunoreactive perikarya in the preoptic area and their dendrites receive appositions from KPLS axons. OVX adult Kiss1-Cre/ZsGreen mice treated for 4 d with 17β-estradiol or vehicle were used for RNA sequencing studies of laser-microdissected KPLS neurons. The transcriptome included markers of GABAergic and neuropeptidergic (Penk, Cartpt, Vgf) cotransmission and 571 estrogen-regulated transcripts. Estrogen treatment upregulated the acetylcholine receptor transcript Chrm2 and, in slice electrophysiology experiments, caused enhanced muscarinic inhibition of KPLS neurons. Finally, we provided immunohistochemical evidence for homologous neurons in the postmortem human brain, suggesting that KPLS neurons may contribute to evolutionarily conserved regulatory mechanisms. Future studies will need to investigate the putative roles of KPLS neurons in the estrogen-dependent control of GnRH neurons and/or various hypothalamic/limbic functions.

The regulative role and mechanism of BNST in anxiety disorder

Anxiety disorders, common yet impactful emotional disturbances, significantly affect physical and mental health globally. Many neuron circuits are associated with anxiety regulation like septo-hippocampal loop, amygdala(AMYG), bed nucleus of the stria terminalis (BNST), ventral hippocampus (vHPC), and brain regions like medial prefrontal cortex (mPFC). However, the concrete mechanism of anxiety disorder in BNST is relatively unknown. Recent research showed BNST plays a critical role in modulating anxiety owing to its anatomical location and special circuit characteristics, which are considered to be a hub in the limbic system regulating anxiety. BNST consists with multiple subregions, which can project separately into different brain regions and exert projecting independently to various brain regions with distinct regulatory effects. Moreover, multiple signal pathways in BNST are reported to play significant roles in regulating anxiety and stress behavior. This review briefly describes anxiety disorders and subdivisions and functions of BNST, focusing on the main neural circuits that serve as fundamental pathways in both the genesis and potential treatment of anxiety disorders and the molecular mechanism of BNST on anxiety. The complexity of structures and mechanisms has facilitated the development of imaging techniques. Innovative multimodal imaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), have non-invasively illuminated BNST activities and their functional connections with other brain areas. These methodologies provide a deeper understanding of how BNST responds to anxiety-inducing stimuli, offering invaluable insights into its complex role in anxiety regulation. The continued exploration of BNST in anxiety research promises not only to elucidate fundamental neurobiological mechanisms but also to foster advancements in clinical treatments for anxiety disorders.

Comprehensive chemotyping, and the gonadal regulation, of seven kisspeptinergic neuronal populations in the mouse brain

BACKGROUND

Kisspeptinergic signaling is well-established as crucial for regulation of reproduction, but its potential broader role in brain function is less understood. This study investigates the distribution and chemotyping of kisspeptin-expressing neurons within the mouse brain.

METHODS

RNAscope singleplex, duplex and multiplex in situ hybridization methods were used to assess kisspeptin mRNA (Kiss1) expression and its co-expression with other neuropeptides, excitatory and inhibitory neurotransmitter markers, and sex steroid receptors in intact and gonadectomized young adult mice.

RESULTS

Seven distinct kisspeptin neuronal chemotypes were characterized, including within two novel Kiss1-expressing groups described here for the first time: the ventral premammillary nucleus, and the nucleus of the solitary tract. Kiss1 mRNA was also localized in the soma, and within the dendritic compartment, of hypothalamic neurons. Altered Kiss1 expression following gonadectomy suggests a previously unappreciated role for androgen receptors in regulating kisspeptin signaling.

CONCLUSION

This study provides a detailed chemoanatomical map of kisspeptin-expressing neurons in the brain, highlighting their potential functional diversity. The discovery of new kisspeptin-expressing neuronal populations, and gonadectomy-induced changes in Kiss1 expression patterns, provide a basis for further exploration of non-endocrine roles for kisspeptin in brain function.

Selective depletion of kisspeptin neurons in the hypothalamic arcuate nucleus in early juvenile life reduces pubertal LH secretion and delays puberty onset in mice

Puberty is the critical developmental transition to reproductive capability driven by the activation of gonadotropin-releasing hormone (GnRH) neurons. The complex neural mechanisms underlying pubertal activation of GnRH secretion still remain unknown, yet likely include kisspeptin neurons. However, kisspeptin neurons reside in several hypothalamic areas and the specific kisspeptin population timing pubertal onset remains undetermined. To investigate this, we strategically capitalized on the differential ontological expression of the Kiss1 gene in different hypothalamic nuclei to selectively ablate just arcuate kisspeptin neurons (aka KNDy neurons) during the early juvenile period, well before puberty, while sparing RP3V kisspeptin neurons. Both male and female transgenic mice with a majority of their KNDy neurons ablated (KNDyABL) by diphtheria toxin treatment in juvenile life demonstrated significantly delayed puberty onset and lower peripubertal LH secretion than controls. In adulthood, KNDyABL mice demonstrated normal in vivo LH pulse frequency with lower basal and peak LH levels, suggesting that only a small subset of KNDy neurons is sufficient for normal GnRH pulse timing but more KNDy cells are needed to secrete normal LH concentrations. Unlike prior KNDy ablation studies in rats, there was no alteration in the occurrence or magnitude of estradiol-induced LH surges in KNDyABL female mice, indicating that a complete KNDy neuronal population is not essential for normal LH surge generation. This study teases apart the contributions of different kisspeptin neural populations to the control of puberty onset, demonstrating that a majority of KNDy neurons in the arcuate nucleus are necessary for the proper timing of puberty in both sexes.

Social isolation and aggression training lead to escalated aggression and hypothalamus-pituitary-gonad axis hyperfunction in mice

Although the participation of sex hormones and sex hormone-responsive neurons in aggressive behavior has been extensively studied, the role of other systems within the hypothalamus-pituitary-gonadal (HPG) axis remains elusive. Here we assessed how the gonadotropin-releasing hormone (GnRH) and kisspeptin systems are impacted by escalated aggression in male mice. We used a combination of social isolation and aggression training (IST) to exacerbate mice's aggressive behavior. Next, low-aggressive (group-housed, GH) and highly aggressive (IST) mice were compared regarding neuronal activity in the target populations and hormonal levels, using immunohistochemistry and ELISA, respectively. Finally, we used pharmacological and viral approaches to manipulate neuropeptide signaling and expression, subsequently evaluating its effects on behavior. IST mice exhibited enhanced aggressive behavior compared to GH controls, which was accompanied by elevated neuronal activity in GnRH neurons and arcuate nucleus kisspeptin neurons. Remarkably, IST mice presented an increased number of kisspeptin neurons in the anteroventral periventricular nucleus (AVPV). In addition, IST mice exhibited elevated levels of luteinizing hormone (LH) in serum. Accordingly, activation and blockade of GnRH receptors (GnRHR) exacerbated and reduced aggression, respectively. Surprisingly, kisspeptin had intricate effects on aggression, i.e., viral ablation of AVPV-kisspeptin neurons impaired the training-induced rise in aggressive behavior whereas kisspeptin itself strongly reduced aggression in IST mice. Our results indicate that IST enhances aggressive behavior in male mice by exacerbating HPG-axis activity. Particularly, increased GnRH neuron activity and GnRHR signaling were found to underlie aggression whereas the relationship with kisspeptin remains puzzling.

Lateral septum as a possible regulatory center of maternal behaviors

The lateral septum (LS) is involved in controlling anxiety, aggression, feeding, and other motivated behaviors. Lesion studies have also implicated the LS in various forms of caring behaviors. Recently, novel experimental tools have provided a more detailed insight into the function of the LS, including the specific role of distinct cell types and their neuronal connections in behavioral regulations, in which the LS participates. This article discusses the regulation of different types of maternal behavioral alterations using the distributions of established maternal hormones such as prolactin, estrogens, and the neuropeptide oxytocin. It also considers the distribution of neurons activated in mothers in response to pups and other maternal activities, as well as gene expressional alterations in the maternal LS. Finally, this paper proposes further research directions to keep up with the rapidly developing knowledge on maternal behavioral control in other maternal brain regions.

Bed nuclei of the stria terminalis: A key hub in the modulation of anxiety

The bed nuclei of the stria terminalis (BST) is recognised as a pivotal integrative centre for monitoring emotional valence. It is implicated in the regulation of diverse affective states and motivated behaviours, and decades of research have firmly established its critical role in anxiety-related behavioural processes. Researchers have recently intricately dissected the BST's dynamic activities, its connection patterns and its functions with respect to specific cell types using multiple techniques such as optogenetics, in vivo calcium imaging and transgenic tools to unmask the complex circuitry mechanisms that underlie anxiety. In this review, we principally focus on studies of anxiety-involved neuromodulators within the BST and provide a comprehensive architecture of the anxiety network-highlighting the BST as a key hub in orchestrating anxiety-like behaviour. We posit that these promising efforts will contribute to the identification of an accurate roadmap for future treatment of anxiety disorders.

The molecular phenotype of kisspeptin neurons in the medial amygdala of female mice

Reproduction is regulated through the hypothalamic-pituitary-gonadal (HPG) axis, largely via the action of kisspeptin neurons in the hypothalamus. Importantly, Kiss1 neurons have been identified in other brain regions, including the medial amygdala (MeA). Though the MeA is implicated in regulating aspects of both reproductive physiology and behavior, as well as non-reproductive processes, the functional roles of MeA Kiss1 neurons are largely unknown. Additionally, besides their stimulation by estrogen, little is known about how MeA Kiss1 neurons are regulated. Using a RiboTag mouse model in conjunction with RNA-seq, we examined the molecular profile of MeA Kiss1 neurons to identify transcripts that are co-expressed in MeA Kiss1 neurons of female mice and whether these transcripts are modulated by estradiol (E2) treatment. RNA-seq identified >13,800 gene transcripts co-expressed in female MeA Kiss1 neurons, including genes for neuropeptides and receptors implicated in reproduction, metabolism, and other neuroendocrine functions. Of the >13,800 genes co-expressed in MeA Kiss1 neurons, only 45 genes demonstrated significantly different expression levels due to E2 treatment. Gene transcripts such as Kiss1, Gal, and Oxtr increased in response to E2 treatment, while fewer transcripts, such as Esr1 and Cyp26b1, were downregulated by E2. Dual RNAscope and immunohistochemistry was performed to validate co-expression of MeA Kiss1 with Cck and Cartpt. These results are the first to establish a profile of genes actively expressed by MeA Kiss1 neurons, including a subset of genes regulated by E2, which provides a useful foundation for future investigations into the regulation and function of MeA Kiss1 neurons.

Neuroendocrine mechanisms underlying estrogen positive feedback and the LH surge

A fundamental principle in reproductive neuroendocrinology is sex steroid feedback: steroid hormones secreted by the gonads circulate back to the brain to regulate the neural circuits governing the reproductive neuroendocrine axis. These regulatory feedback loops ultimately act to modulate gonadotropin-releasing hormone (GnRH) secretion, thereby affecting gonadotropin secretion from the anterior pituitary. In females, rising estradiol (E₂) during the middle of the menstrual (or estrous) cycle paradoxically "switch" from being inhibitory on GnRH secretion ("negative feedback") to stimulating GnRH release ("positive feedback"), resulting in a surge in GnRH secretion and a downstream LH surge that triggers ovulation. While upstream neural afferents of GnRH neurons, including kisspeptin neurons in the rostral hypothalamus, are proposed as critical loci of E₂ feedback action, the underlying mechanisms governing the shift between E₂ negative and positive feedback are still poorly understood. Indeed, the precise cell targets, neural signaling factors and receptors, hormonal pathways, and molecular mechanisms by which ovarian-derived E₂ indirectly stimulates GnRH surge secretion remain incompletely known. In many species, there is also a circadian component to the LH surge, restricting its occurrence to specific times of day, but how the circadian clock interacts with endocrine signals to ultimately time LH surge generation also remains a major gap in knowledge. Here, we focus on classic and recent data from rodent models and discuss the consensus knowledge of the neural players, including kisspeptin, the suprachiasmatic nucleus, and glia, as well as endocrine players, including estradiol and progesterone, in the complex regulation and generation of E₂-induced LH surges in females.

Kisspeptin neuron electrophysiology: Intrinsic properties, hormonal modulation, and regulation of homeostatic circuits

The obligatory role of kisspeptin (KISS1) and its receptor (KISS1R) in regulating the hypothalamic-pituitary-gonadal axis, puberty and fertility was uncovered in 2003. In the few years that followed, an impressive body of work undertaken in many species established that neurons producing kisspeptin orchestrate gonadotropin-releasing hormone (GnRH) neuron activity and subsequent GnRH and gonadotropin hormone secretory patterns, through kisspeptin-KISS1R signaling, and mediate many aspects of gonadal steroid hormone feedback regulation of GnRH neurons. Here, we review knowledge accrued over the past decade, mainly in genetically modified mouse models, of the electrophysiological properties of kisspeptin neurons and their regulation by hormonal feedback. We also discuss recent progress in our understanding of the role of these cells within neuronal circuits that control GnRH neuron activity and GnRH secretion, energy balance and, potentially, other homeostatic and reproductive functions.

Progesterone Receptors in AVPV Kisspeptin Neurons Are Sufficient for Positive Feedback Induction of the LH Surge

Kisspeptin, encoded by Kiss1, stimulates gonadotropin-releasing hormone neurons to govern reproduction. In female rodents, estrogen-sensitive kisspeptin neurons in the rostral anteroventral periventricular (AVPV) hypothalamus are thought to mediate estradiol (E2)-induced positive feedback induction of the preovulatory luteinizing hormone (LH) surge. AVPV kisspeptin neurons coexpress estrogen and progesterone receptors (PGRs) and are activated during the LH surge. While E2 effects on kisspeptin neurons have been well studied, progesterone's regulation of kisspeptin neurons is less understood. Using transgenic mice lacking PGR exclusively in kisspeptin cells (termed KissPRKOs), we previously demonstrated that progesterone action specifically in kisspeptin cells is essential for ovulation and normal fertility. Unlike control females, KissPRKO females did not generate proper LH surges, indicating that PGR signaling in kisspeptin cells is required for positive feedback. However, because PGR was knocked out from all kisspeptin neurons in the brain, that study was unable to determine the specific kisspeptin population mediating PGR action on the LH surge. Here, we used targeted Cre-mediated adeno-associated virus (AAV) technology to reintroduce PGR selectively into AVPV kisspeptin neurons of adult KissPRKO females, and tested whether this rescues occurrence of the LH surge. We found that targeted upregulation of PGR in kisspeptin neurons exclusively in the AVPV is sufficient to restore proper E2-induced LH surges in KissPRKO females, suggesting that this specific kisspeptin population is a key target of the necessary progesterone action for the surge. These findings further highlight the critical importance of progesterone signaling, along with E2 signaling, in the positive feedback induction of LH surges and ovulation.

Functions of galanin, spexin and kisspeptin in metabolism, mood and behaviour

The bioactive peptides galanin, spexin and kisspeptin have a common ancestral origin and their pathophysiological roles are increasingly the subject of investigation. Evidence suggests that these bioactive peptides play a role in the regulation of metabolism, pancreatic β-cell function, energy homeostasis, mood and behaviour in several species, including zebrafish, rodents and humans. Galanin signalling suppresses insulin secretion in animal models (but not in humans), is potently obesogenic and plays putative roles governing certain evolutionary behaviours and mood modulation. Spexin decreases insulin secretion and has potent anorectic, analgesic, anxiolytic and antidepressive-like effects in animal models. Kisspeptin modulates glucose-stimulated insulin secretion, food intake and/or energy expenditure in animal models and humans. Furthermore, kisspeptin is implicated in the control of reproductive behaviour in animals, modulation of human sexual and emotional brain processing, and has antidepressive and fear-suppressing effects. In addition, galanin-like peptide is a further member of the galaninergic family that plays emerging key roles in metabolism and behaviour. Therapeutic interventions targeting galanin, spexin and/or kisspeptin signalling pathways could therefore contribute to the treatment of conditions ranging from obesity to mood disorders. However, many gaps and controversies exist, which must be addressed before the therapeutic potential of these bioactive peptides can be established.

The human hypothalamic kisspeptin system: Functional neuroanatomy and clinical perspectives

In mammals, kisspeptin neurons are the key components of the hypothalamic neuronal networks that regulate the onset of puberty, account for the pulsatile secretion of gonadotropin-releasing hormone (GnRH) and mediate negative and positive estrogen feedback signals to GnRH neurons. Being directly connected anatomically and functionally to the hypophysiotropic GnRH system, the major kisspeptin cell groups of the preoptic area/rostral hypothalamus and the arcuate (or infundibular) nucleus, respectively, are ideally positioned to serve as key nodes which integrate various types of environmental, endocrine, and metabolic signals that can influence fertility. This chapter provides an overview of the current state of knowledge on the anatomy, functions, and plasticity of brain kisspeptin systems based on the wide literature available from different laboratory and domestic species. Then, the species-specific features of human hypothalamic kisspeptin neurons are described, covering their topography, morphology, unique neuropeptide content, plasticity, and connectivity to hypophysiotropic GnRH neurons. Some newly emerging roles of central kisspeptin signaling in behavior and finally, clinical perspectives, are discussed.

Unraveling the connection between GABA and kisspeptin in the control of reproduction

Neuroendocrine control of reproduction involves the interplay of various factors that become active at some point along development. GnRH is the main neurohormone controlling reproduction and among the most important inputs modulating GnRH synthesis/secretion are GABA and kisspeptins. These interactions of GABA and kisspeptin in the control of GnRH secretion can take place by the presence of the receptors of both factors on the GnRH neuron or alternatively by the actions of GABA on kisspeptin neurons and/or the actions of kisspeptin on GABA neurons. Kisspeptin acts on the Kiss1R, a seven transmembrane domain, Gαq/11-coupled receptor that activates phospholipase C, although some Gαq/11-independent pathways in mediating part of the effects of Kiss1R activation have also been proposed. GABA acts through two kinds of receptors, ionotropic GABAA/C receptors involving a chloride channel and associated with fast inhibitory/stimulatory conductance and metabotropic GABAB receptors (GABABR) that are Gi/0 protein linked inducing late slow hyperpolarization. In this review, we aim to summarize the different ways in which these two actors, kisspeptin and GABA, interact to modulate GnRH secretion across the reproductive lifespan.

Dietary phytoestrogens modulate aggression and activity in social behavior circuits of male mice

Phytoestrogens comprise biologically active constituents of human and animal diet that can impact on systemic and local estrogen functions in the brain. Here we report on the importance of dietary phytoestrogens for maintaining activity in a brain circuit controlling aggressive and social behavior of male mice. After six weeks of low-phytoestrogen chronic diet (diadzein plus genistein <20 μg/g) a reduction of intermale aggression and altered territorial marking behavior could be observed, compared to littermates on a standard soy-bean based diet (300 μg/g). Further, mice on low-phyto diet displayed a decrease in sociability and a reduced preference for social odors, indicating a general disturbance of social behavior. Underlying circuits were investigated by analysing the induction of the activity marker c-Fos upon social encounter. Low-phyto diet led to a markedly reduced c-Fos induction in the medial as well as the cortical amygdala, the lateral septum, medial preoptic area and bed nucleus of the stria terminalis. No difference between groups was observed in the olfactory bulb. Together our data suggest that dietary phytoestrogens critically modulate social behavior circuits in the male mouse brain.

The Role of the Brain in the Pathogenesis and Physiology of Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder, affecting at least 10% of women of reproductive age. PCOS is typically characterized by the presence of at least two of the three cardinal features of hyperandrogenemia (high circulating androgen levels), oligo- or anovulation, and cystic ovaries. Hyperandrogenemia increases the severity of the condition and is driven by increased luteinizing hormone (LH) pulse secretion from the pituitary. Indeed, PCOS women display both elevated mean LH levels, as well as an elevated frequency of LH pulsatile secretion. The abnormally high LH pulse frequency, reflective of a hyperactive gonadotropin-releasing hormone (GnRH) neural circuit, suggests a neuroendocrine basis to either the etiology or phenotype of PCOS. Several studies in preclinical animal models of PCOS have demonstrated alterations in GnRH neurons and their upstream afferent neuronal circuits. Some rodent PCOS models have demonstrated an increase in GnRH neuron activity that correlates with an increase in stimulatory GABAergic innervation and postsynaptic currents onto GnRH neurons. Additional studies have identified robust increases in hypothalamic levels of kisspeptin, another potent stimulator of GnRH neurons. This review outlines the different brain and neuroendocrine changes in the reproductive axis observed in PCOS animal models, discusses how they might contribute to either the etiology or adult phenotype of PCOS, and considers parallel findings in PCOS women.