Feedback Loops Link Odor and Pheromone Signaling with Reproduction

Participation of kisspeptin, progesterone, and GnRH receptors on lordosis behavior induced by kisspeptin

The neuropeptide kisspeptin (Kiss) is crucial in regulating the hypothalamic-pituitary-gonadal axis. It is produced by two main groups of neurons in the hypothalamus: the rostral periventricular region around the third ventricle and the arcuate nucleus. Kiss is the peptide product of the KiSS-1 gene and serves as the endogenous agonist for the GPR54 receptor. The Kiss/GPR54 system functions as a critical regulator of the reproductive system. Thus, we examined the effect of intracerebroventricular administration of 3 μg of Kiss to the right lateral ventricle of ovariectomized rats primed with a dose of 5 μg subcutaneous (sc) of estradiol benzoate (EB). Kiss treatment increased the lordosis quotient at all times tested. However, the lordosis reflex score was comparatively lower yet still significant compared to the control group. To investigate receptor specificity and downstream mechanisms on lordosis, we infused 10 μg of GPR54 receptor antagonist, Kiss-234, 5 μg of the progestin receptor antagonist, RU486, or 3 μg of antide, a gonadotropin-releasing hormone-1 (GnRH-1) receptor antagonist, to the right lateral ventricle 30 min before an infusion of 3 μg of Kiss. Results demonstrated a significant reduction in the facilitation of lordosis behavior by Kiss at 60 and 120 min when Kiss-234, RU486, or antide were administered. These findings suggest that Kiss stimulates lordosis expression by activating GPR54 receptors on GnRH neurons and that Kiss/GPR54 system is an essential intermediary by which progesterone activates GnRH.

A GnRH neuronal population in the olfactory bulb translates socially relevant odors into reproductive behavior in male mice

Hypothalamic gonadotropin-releasing hormone (GnRH) neurons regulate fertility and integrate hormonal status with environmental cues to ensure reproductive success. Here we show that GnRH neurons in the olfactory bulb (GnRHOB) of adult mice can mediate social recognition. Specifically, we show that GnRHOB neurons extend neurites into the vomeronasal organ and olfactory epithelium and project to the median eminence. GnRHOB neurons in males express vomeronasal and olfactory receptors, are activated by female odors and mediate gonadotropin release in response to female urine. Male preference for female odors required the presence and activation of GnRHOB neurons, was impaired after genetic inhibition or ablation of these cells and relied on GnRH signaling in the posterodorsal medial amygdala. GnRH receptor expression in amygdala kisspeptin neurons appear to be required for GnRHOB neurons' actions on male mounting behavior. Taken together, these results establish GnRHOB neurons as regulating fertility, sex recognition and mating in male mice.

Glutamate neurotransmission from leptin receptor cells is required for typical puberty and reproductive function in female mice

The hypothalamic ventral premammillary nucleus (PMv) is a glutamatergic nucleus essential for the metabolic control of reproduction. However, conditional deletion of leptin receptor long form (LepRb) in vesicular glutamate transporter 2 (Vglut2) expressing neurons results in virtually no reproductive deficits. In this study, we determined the role of glutamatergic neurotransmission from leptin responsive PMv neurons on puberty and fertility. We first assessed if stimulation of PMv neurons induces luteinizing hormone (LH) release in fed adult females. We used the stimulatory form of designer receptor exclusively activated by designer drugs (DREADDs) in LeprCre (LepRb-Cre) mice. We collected blood sequentially before and for 1 hr after intravenous clozapine-N-oxide injection. LH level increased in animals correctly targeted to the PMv, and LH level was correlated to the number of Fos immunoreactive neurons in the PMv. Next, females with deletion of Slc17a6 (Vglut2) in LepRb neurons (LeprΔVGlut2) showed delayed age of puberty, disrupted estrous cycles, increased gonadotropin-releasing hormone (GnRH) concentration in the axon terminals, and disrupted LH secretion, suggesting impaired GnRH release. To assess if glutamate is required for PMv actions in pubertal development, we generated a Cre-induced reexpression of endogenous LepRb (LeprloxTB) with concomitant deletion of Slc17a6 (Vglut2flox) mice. Rescue of Lepr and deletion of Slc17a6 in the PMv was obtained by stereotaxic injection of an adeno-associated virus vector expressing Cre recombinase. Control LeprloxTB mice with PMv LepRb rescue showed vaginal opening, follicle maturation, and became pregnant, while LeprloxTB;Vglut2flox mice showed no pubertal development. Our results indicate that glutamatergic neurotransmission from leptin sensitive neurons regulates the reproductive axis, and that leptin action on pubertal development via PMv neurons requires Vglut2.

Kisspeptin administration may promote precopulatory behavior in male rats independently or supplementally to testosterone and contribute to proceptive behavior in female partners, reducing mating failure

Kisspeptin is a peptide that plays an important role through its effects on the hypothalamus-pituitary-gonadal (HPG) axis. It has also been implicated in sexual behavior. The present study investigated whether the relationship between kisspeptin and sexual behavior is independent of the HPG axis, i.e., testosterone. Sexual behavior was examined after the administration of kisspeptin to gonadally intact male rats and gonadectomized male rats that received testosterone supplementation. Other male rats were also observed for sexual behavior once a week from 2 to 5 weeks after gonadectomy and receiving kisspeptin for the sixth postoperative week. Sexual behavior in female rats serving as the partner for each male was also observed. Female rats were not administered kisspeptin in the present study. The results obtained showed that the administration of kisspeptin increased precopulatory behavior in gonadally intact male rats and gonadectomized male rats that received testosterone supplementation and proceptive behavior in their female partners. Precopulatory behavior in males and receptive behavior in females increased, while copulatory behavior in males and receptive behavior in females remained unchanged. Furthermore, the administration of kisspeptin increased precopulatory behavior in gonadectomized males, but did not affect receptive behavior in females. These results suggest that kisspeptin affected males independently and/or supplementally to testosterone, and also that changes in the presence of testosterone in males had an impact on proceptive behavior in their female partners. In conclusion, kisspeptin may involve an as-yet-unidentified neural pathway in sexual desire independently of the HPG axis.

Glutamate neurotransmission from leptin receptor cells is required for typical puberty and reproductive function in female mice

The hypothalamic ventral premammillary nucleus (PMv) is a glutamatergic nucleus essential for the metabolic control of reproduction. However, conditional deletion of leptin receptor (LepRb) in vesicular glutamate transporter 2 (Vglut2) expressing neurons results in virtually no reproductive deficits. In this study, we determine the role of glutamatergic signaling from leptin responsive PMv neurons on puberty and fertility. We first assessed if stimulation of PMv neurons induces LH release in fed adult females. We used the stimulatory form of designer receptor exclusively activated by designer drugs (DREADDs) in LepRb-Cre mice. We collected blood sequentially before and for 1h after iv. clozapine-N-oxide injection. LH level increased in animals correctly targeted to the PMv, and LH level was correlated to the number of cFos immunoreactive neurons in the PMv. Next, females with deletion of Vglut2 in LepRb neurons (LepR∆VGlut2) showed delayed age of puberty, disrupted estrous cycles, increased GnRH concentration in the axon terminals and disrupted LH responses, suggesting impaired GnRH release. To assess if glutamate is required for PMv actions in pubertal development, we generated a Cre-induced reexpression of endogenous LepRb (LepRloxTB) with concomitant deletion of Vglut2 (Vglut2-floxed) mice. Rescue of Lepr and deletion of Vglut2 in the PMv was obtained by stereotaxic injection of an adeno-associated virus vector expressing Cre recombinase. Control LepRloxTB mice with PMv LepRb rescue showed vaginal opening, follicle maturation and became pregnant, while LepRloxTB;Vglut2flox mice showed no pubertal development. Our results indicate that glutamatergic signaling from leptin sensitive neurons regulates the reproductive axis, and that leptin action on pubertal development via PMv neurons requires Vglut2.

Genomic regions and biological pathways associated with sex-limited reproductive traits in bovine species

Many animal species exhibit sex-limited traits, where certain phenotypes are exclusively expressed in one sex. Yet, the genomic regions that contribute to these sex-limited traits in males and females remain a subject of debate. Reproductive traits are ideal phenotypes to study sexual differences since they are mostly expressed in a sex-limited way. Therefore, this study aims to use local correlation analyses to identify genomic regions and biological pathways significantly associated with male and female sex-limited traits in two distinct cattle breeds (Brahman [BB] and Tropical Composite [TC]). We used the Correlation Scan method to perform local correlation analysis on 42 trait pairs consisting of six female and seven male reproductive traits recorded on ~1,000 animals for each sex in each breed. To pinpoint a specific region associated with these sex-limited reproductive traits, we investigated the genomic region(s) consistently identified as significant across the 42 trait pairs in each breed. The genes found in the identified regions were subjected to Quantitative Trait Loci (QTL) colocalization, QTL enrichment analyses, and functional analyses to gain biological insight into sexual differences. We found that the genomic regions associated with the sex-limited reproductive phenotypes are widely distributed across all the chromosomes. However, no single region across the genome was associated with all the 42 reproductive trait pairs in the two breeds. Nevertheless, we found a region on the X-chromosome to be most significant for 80% to 90% (BB: 33 and TC: 38) of the total 42 trait pairs. A considerable number of the genes in this region were regulatory genes. By considering only genomic regions that were significant for at least 50% of the 42 trait pairs, we observed more regions spread across the autosomes and the X-chromosome. All genomic regions identified were highly enriched for trait-specific QTL linked to sex-limited traits (percentage of normal sperm, metabolic weight, average daily gain, carcass weight, age at puberty, etc.). The gene list created from these identified regions was enriched for biological pathways that contribute to the observed differences between sexes. Our results demonstrate that genomic regions associated with male and female sex-limited reproductive traits are distributed across the genome. Yet, chromosome X seems to exert a relatively larger effect on the phenotypic variation observed between the sexes.

Specific sensory neurons and insulin-like peptides modulate food type-dependent oogenesis and fertilization in Caenorhabditis elegans

An animal's responses to environmental cues are critical for its reproductive program. Thus, a mechanism that allows the animal to sense and adjust to its environment should make for a more efficient reproductive physiology. Here, we demonstrate that in Caenorhabditis elegans specific sensory neurons influence onset of oogenesis through insulin signaling in response to food-derived cues. The chemosensory neurons ASJ modulate oogenesis onset through the insulin-like peptide (ILP) INS-6. In contrast, other sensory neurons, the olfactory neurons AWA, regulate food type-dependent differences in C. elegans fertilization rates, but not onset of oogenesis. AWA modulates fertilization rates at least partly in parallel to insulin receptor signaling, since the insulin receptor DAF-2 regulates fertilization independently of food type, which requires ILPs other than INS-6. Together our findings suggest that optimal reproduction requires the integration of diverse food-derived inputs through multiple neuronal signals acting on the C. elegans germline.

Mechanisms linking neurological disorders with reproductive endocrine dysfunction: Insights from epilepsy research

Gonadal hormone actions in the brain can both worsen and alleviate symptoms of neurological disorders. Although neurological conditions and reproductive endocrine function are seemingly disparate, compelling evidence indicates that reciprocal interactions exist between certain disorders and hypothalamic-pituitary-gonadal (HPG) axis irregularities. Epilepsy is a neurological disorder that shows significant reproductive endocrine dysfunction (RED) in clinical populations. Seizures, particularly those arising from temporal lobe structures, can drive HPG axis alterations, and hormones produced in the HPG axis can reciprocally modulate seizure activity. Despite this relationship, mechanistic links between seizures and RED, and vice versa, are still largely unknown. Here, we review clinical evidence alongside recent investigations in preclinical animal models into the contributions of seizures to HPG axis malfunction, describe the effects of HPG axis hormonal feedback on seizure activity, and discuss how epilepsy research can offer insight into mechanisms linking neurological disorders to HPG axis dysfunction, an understudied area of neuroendocrinology.

Neural control of female sexual behaviors

Reproduction is the biological process by which new individuals are produced by their parents. It is the fundamental feature of all known life and is required for the existence of all species. All mammals reproduce sexually, a process that involves the union of two reproductive cells, one from a male and one from a female. Sexual behaviors are a series of actions leading to reproduction. They are composed of appetitive, action, and refractory phases, each supported by dedicated developmentally-wired neural circuits to ensure high reproduction success. In rodents, successful reproduction can only occur during female ovulation. Thus, female sexual behavior is tightly coupled with ovarian activity, namely the estrous cycle. This is achieved through the close interaction between the female sexual behavior circuit and the hypothalamic-pituitary-gonadal (HPG) axis. In this review, we will summarize our current understanding, learned mainly in rodents, regarding the neural circuits underlying each phase of the female sexual behaviors and their interaction with the HPG axis, highlighting the gaps in our knowledge that require future investigation.

Olfactory and neuropeptide inputs to appetite neurons in the arcuate nucleus

The sense of smell has potent effects on appetite, but the underlying neural mechanisms are largely a mystery. The hypothalamic arcuate nucleus contains two subsets of neurons linked to appetite: AgRP (agouti-related peptide) neurons, which enhance appetite, and POMC (pro-opiomelanocortin) neurons, which suppress appetite. Here, we find that AgRP and POMC neurons receive indirect inputs from partially overlapping areas of the olfactory cortex, thus identifying their sources of odor signals. We also find neurons directly upstream of AgRP or POMC neurons in numerous other areas, identifying potential relays between the olfactory cortex and AgRP or POMC neurons. Transcriptome profiling of individual AgRP neurons reveals differential expression of receptors for multiple neuromodulators. Notably, known ligands of the receptors define subsets of neurons directly upstream of AgRP neurons in specific brain areas. Together, these findings indicate that higher olfactory areas can differentially influence AgRP and POMC appetite neurons, that subsets of AgRP neurons can be regulated by different neuromodulators, and that subsets of neurons upstream of AgRP neurons in specific brain areas use different neuromodulators, together or in distinct combinations to modulate AgRP neurons and thus appetite.

Reciprocal relationships between sleep and smell

Despite major anatomical differences with other mammalian sensory systems, olfaction shares with those systems a modulation by sleep/wake states. Sleep modulates odor sensitivity and serves as an important regulator of both perceptual and associative odor memory. In addition, however, olfaction also has an important modulatory impact on sleep. Odors can affect the latency to sleep onset, as well as the quality and duration of sleep. Olfactory modulation of sleep may be mediated by direct synaptic interaction between the olfactory system and sleep control nuclei, and/or indirectly through odor modulation of arousal and respiration. This reciprocal interaction between sleep and olfaction presents novel opportunities for sleep related modulation of memory and perception, as well as development of non-pharmacological olfactory treatments of simple sleep disorders.

The role of ciliopathy-associated type 3 adenylyl cyclase in infanticidal behavior in virgin adult male mice

Virgin adult male mice often display killing of alien newborns, defined as infanticide, and this behavior is dependent on olfactory signaling. Olfactory perception is achieved by the main olfactory system (MOS) or vomeronasal system (VNS). Although it has been established that the VNS is crucial for infanticide in male mice, the role of the MOS in infanticide remains unknown. Herein, by producing lesions via ZnSO₄ perfusion and N-methyl-D-aspartic acid stereotactic injection, we demonstrated that the main olfactory epithelium (MOE), anterior olfactory nucleus (AON), or ventromedial hypothalamus (VMH) is crucial for infanticide in adult males. By using CRISPR-Cas9 coupled with adeno-associated viruses to induce specific knockdown of type 3 adenylyl cyclase (AC3) in these tissues, we further demonstrated that AC3, a ciliopathy-associated protein, in the MOE and the expression of related proteins in the AON or VMH are necessary for infanticidal behavior in virgin adult male mice.

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MOE lesions and knockdown of AC3 in the MOE result in abnormal infanticidal behavior

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The infanticidal behavior of male mice is impaired by lesioning of the AON or VMH

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AC3 knockdown in the AON or VMH affects the infanticidal behavior of male mice

Quantitative proteomics analysis to assess protein expression levels in the ovaries of pubescent goats

Background

Changes in the abundance of ovarian proteins play a key role in the regulation of reproduction. However, to date, no studies have investigated such changes in pubescent goats. Herein we applied isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography–tandem mass spectrometry to analyze the expression levels of ovarian proteins in pre-pubertal (n = 3) and pubertal (n = 3) goats.

Results

Overall, 7,550 proteins were recognized; 301 (176 up- and 125 downregulated) were identified as differentially abundant proteins (DAPs). Five DAPs were randomly selected for expression level validation by Western blotting; the results of Western blotting and iTRAQ analysis were consistent. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that DAPs were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways. Besides, gene ontology functional enrichment analysis revealed that several DAPs enriched in biological processes were associated with cellular process, biological regulation, metabolic process, and response to stimulus. Protein–protein interaction network showed that proteins interacting with CDK1, HSPA1A, and UCK2 were the most abundant.

Conclusions

We identified 301 DAPs, which were enriched in olfactory transduction, glutathione metabolism, and calcium signaling pathways, suggesting the involvement of these processes in the onset of puberty. Further studies are warranted to more comprehensively explore the function of the identified DAPs and aforementioned signaling pathways to gain novel, deeper insights into the mechanisms underlying the onset of puberty.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08699-y.

Estrogenic regulation of reproduction and energy homeostasis by a triumvirate of hypothalamic arcuate neurons

Pregnancy is energetically demanding and therefore, by necessity, reproduction and energy balance are inextricably linked. With insufficient or excessive energy stores a female is liable to suffer complications during pregnancy or produce unhealthy offspring. Gonadotropin-releasing hormone neurons are responsible for initiating both the pulsatile and subsequent surge release of luteinizing hormone to control ovulation. Meticulous work has identified two hypothalamic populations of kisspeptin (Kiss1) neurons that are critical for this pattern of release. The involvement of the hypothalamus is unsurprising because its quintessential function is to couple the endocrine and nervous systems, coordinating energy balance and reproduction. Estrogens, more specifically 17β-estradiol (E₂ ), orchestrate the activity of a triumvirate of hypothalamic neurons within the arcuate nucleus (ARH) that govern the physiological underpinnings of these behavioral dynamics. Arising from a common progenitor pool, these cells differentiate into ARH kisspeptin, pro-opiomelanocortin (POMC), and agouti related peptide/neuropeptide Y (AgRP) neurons. Although the excitability of all these subpopulations is subject to genomic and rapid estrogenic regulation, Kiss1 neurons are the most sensitive, reflecting their integral function in female fertility. Based on the premise that E₂ coordinates autonomic functions around reproduction, we review recent findings on how Kiss1 neurons interact with gonadotropin-releasing hormone, AgRP and POMC neurons, as well as how the rapid membrane-initiated and intracellular signaling cascades activated by E₂ in these neurons are critical for control of homeostatic functions supporting reproduction. In particular, we highlight how Kiss1 and POMC neurons conspire to inhibit AgRP neurons and diminish food motivation in service of reproductive success.

Assessment of Biostimulation Methods Based on Chemical Communication in Female Doe Reproduction

Biostimulation is an animal management practice that helps improve reproductive parameters by modulating animal sensory systems. Chemical signals, mostly known as pheromones, have a great potential in this regard. This study was conducted to determine the influence of short-term female rabbit exposure to different conditions, mainly pheromone-mediated, on reproductive parameters of inseminated does. Groups of 60 females/each were exposed to (1) female urine, (2) male urine, (3) seminal plasma and (4) female–female (F–F) separated, just before artificial insemination, and compared to a ‘golden method’ female–female interaction. The following reproductive parameters were analyzed for each group: receptivity (vulvar color), fertility (kindling rate), prolificacy and number of born alive and dead kits/litter. Our results showed that the biostimulation methods employed in this experiment did not significantly improve any of the analyzed parameters. However, female doe exposure to urine, especially to male urine, showed no significant higher fertility values (95.4%) when compared to the rest of the experimental conditions (on average 92.4%). Female–female interaction before artificial insemination, which is a common practice in rabbit farms, showed similar results as not establishing social interaction (F–F separated), which suggests that F–F interaction could be replaced by F–F separated, therefore avoiding unnecessary animal management and time cost. On the other hand, fertility ranges were lower for animals with a pale vulvar color whereas no differences were noticed among the other three colors which measure receptivity (pink, red, purple), thus suggesting that these three colors could be grouped together. Future studies should aim at determining potential chemical cues/pheromones released through bodily secretions that influence reproduction in rabbits, therefore contributing to animal welfare and to a natural image of animal production.

Kisspeptin neurons as a key player bridging the endocrine system and sexual behavior in mammals

Reproductive behaviors are sexually differentiated: for example, male rodents show mounting behavior, while females in estrus show lordosis behavior as sex-specific sexual behaviors. Kisspeptin neurons govern reproductive function via direct stimulation of gonadotropin-releasing hormone (GnRH) and subsequent gonadotropin release for gonadal steroidogenesis in mammals. First, we discuss the role of hypothalamic kisspeptin neurons as an indispensable regulator of sexual behavior by stimulating the synthesis of gonadal steroids, which exert "activational effects" on the behavior in adulthood. Second, we discuss the central role of kisspeptin neurons that are directly involved in neural circuits controlling sexual behavior in adulthood. We then focused on the role of perinatal hypothalamic kisspeptin neurons in the induction of perinatal testosterone secretion for its "organizational effects" on masculinization/defeminization of the male brain in rodents during a critical period. We subsequently concluded that kisspeptin neurons are key players in bridging the endocrine system and sexual behavior in mammals.

GnRH neurons recruit astrocytes in infancy to facilitate network integration and sexual maturation

Neurons that produce gonadotropin-releasing hormone (GnRH), which control fertility, complete their nose-to-brain migration by birth. However, their function depends on integration within a complex neuroglial network during postnatal development. Here, we show that rodent GnRH neurons use a prostaglandin D₂ receptor DP1 signaling mechanism during infancy to recruit newborn astrocytes that 'escort' them into adulthood, and that the impairment of postnatal hypothalamic gliogenesis markedly alters sexual maturation by preventing this recruitment, a process mimicked by the endocrine disruptor bisphenol A. Inhibition of DP1 signaling in the infantile preoptic region, where GnRH cell bodies reside, disrupts the correct wiring and firing of GnRH neurons, alters minipuberty or the first activation of the hypothalamic-pituitary-gonadal axis during infancy, and delays the timely acquisition of reproductive capacity. These findings uncover a previously unknown neuron-to-neural-progenitor communication pathway and demonstrate that postnatal astrogenesis is a basic component of a complex set of mechanisms used by the neuroendocrine brain to control sexual maturation.

Understanding the Role of Semiochemicals on the Reproductive Behaviour of Cheetahs (Acinonyx jubatus)-A Review

Simple Summary

This review aims to provide an in-depth overview of the reproductive physiology and behaviour of cheetahs (Acinonyx jubatus). Specifically, it focuses on the role that pheromones (a class of semiochemicals) play by directly affecting the reproductive (e.g., precopulatory and copulatory) behaviour. Furthermore, it aims to critically analyze current research and provide new insights on study areas needing further investigation. It is clear, for instance, that further research is necessary to investigate the role of semiochemicals in the reproductive behaviour of cheetahs in order to rectify the current behavioural difficulties experienced when breeding younger females. This, in turn, would aid in improving captive breeding and the prevention of asymmetric reproductive aging.

Abstract

The cheetah species (Acinonyx jubatus) is currently listed as vulnerable according to the International Union for Conservation of Nature (IUCN). Captive breeding has long since been used as a method of conservation of the species, with the aim to produce a healthy, strong population of cheetahs with an increased genetic variety when compared to their wild counterparts. This would then increase the likelihood of survivability once released into protected areas. Unfortunately, breeding females have been reported to be difficult due to the age of these animals. Older females are less fertile, have more difficult parturition, and are susceptible to asymmetric reproductive aging whereas younger females tend to show a significantly lower frequency of mating behaviour than that of older females, which negatively affects breeding introductions, and therefore mating. Nonetheless, the experience from breeding methods used in some breeding centres in South Africa and the Netherlands, which also rely on the role that semiochemicals play in breeding, proves that cheetahs can be bred successfully in captivity. This review aims to give the reader an in-depth overview of cheetahs’ reproductive physiology and behaviour, focusing on the role that pheromones play in this species. Furthermore, it aims to provide new insight into the use of semiochemicals to improve conservation strategies through captive breeding.

Sexually Dimorphic Neurosteroid Synthesis Regulates Neuronal Activity in the Murine Brain

Sex steroid hormones act on hypothalamic kisspeptin neurons to regulate reproductive neural circuits in the brain. Kisspeptin neurons start to express estrogen receptors in utero, suggesting steroid hormone action on these cells early during development. Whether neurosteroids are locally produced in the embryonic brain and impinge onto kisspeptin/reproductive neural circuitry is not known. To address this question, we analyzed aromatase expression, a key enzyme in estrogen synthesis, in male and female mouse embryos. We identified an aromatase neuronal network comprising ∼6000 neurons in the hypothalamus and amygdala. By birth, this network has become sexually dimorphic in a cluster of aromatase neurons in the arcuate nucleus adjacent to kisspeptin neurons. We demonstrate that male arcuate aromatase neurons convert testosterone to estrogen to regulate kisspeptin neuron activity. We provide spatiotemporal information on aromatase neuronal network development and highlight a novel mechanism whereby aromatase neurons regulate the activity of distinct neuronal populations expressing estrogen receptors.SIGNIFICANCE STATEMENT Sex steroid hormones, such as estradiol, are important regulators of neural circuits controlling reproductive physiology in the brain. Embryonic kisspeptin neurons in the hypothalamus express steroid hormone receptors, suggesting hormone action on these cells in utero Whether neurosteroids are locally produced in the brain and impinge onto reproductive neural circuitry is insufficiently understood. To address this question, we analyzed aromatase expression, a key enzyme in estradiol synthesis, in mouse embryos and identified a network comprising ∼6000 neurons in the brain. By birth, this network has become sexually dimorphic in a cluster of aromatase neurons in the arcuate nucleus adjacent to kisspeptin neurons. We demonstrate that male aromatase neurons convert testosterone to estradiol to regulate kisspeptin neuron activity.

Kisspeptin signaling and nNOS neurons in the VMHvl modulate lordosis behavior but not mate preference in female mice

It was recently shown that kisspeptin neurons in the anteroventral periventricular area (AVPV) orchestrate female sexual behavior, including lordosis behavior and mate preference. A potential target of AVPV kisspeptin signaling could be neurons expressing the neuronal form of nitric oxide synthase (nNOS) in the ventrolateral part of the ventromedial hypothalamus (VMHvl). Therefore, in the present study, we further refined the role of the VHMvl in female sexual behavior. Adult female mice received a bilateral cannula aimed at the VMHvl. A single injection with kisspeptin (Kp-10) or SNAP/BAY, a nitric oxide donor, significantly increased lordosis, whereas the nNOS inhibitor l-NAME decreased it. None of these drugs affected mate preference. Interestingly, administration of GnRH into the VMHvl had no effect on lordosis or mate preference. To determine whether the stimulatory effect of Kp-10 on lordosis was specific to the VMHvl, an additional group of females received Kp-10 directly into the paraventricular nucleus (PVN). No effect was found on lordosis and mate preference. These results suggest that kisspeptin most likely modulates lordosis behavior through nNOS neurons in the VMHvl whereas mate preference is modulated by kisspeptin through a separate neuronal circuit not including the VMHvl.

Multimodal learning of pheromone locations

Memorizing pheromonal locations is critical for many mammalian species as it involves finding mates and avoiding competitors. In rodents, pheromonal information is perceived by the main and accessory olfactory systems. However, the role of somatosensation in context-dependent learning and memorizing of pheromone locations remains unexplored. We addressed this problem by training female mice on a multimodal task to locate pheromones by sampling volatiles emanating from male urine through the orifices of varying dimensions or shapes that are sensed by their vibrissae. In this novel pheromone location assay, female mice’ preference toward male urine scent decayed over time when they were permitted to explore pheromones vs neutral stimuli, water. On training them for the associations involving olfactory and whisker systems, it was established that they were able to memorize the location of opposite sex pheromones, when tested 15 days later. This memory was not formed either when the somatosensory inputs through whisker pad were blocked or when the pheromonal cues were replaced with that of same sex. The association between olfactory and somatosensory systems was further confirmed by the enhanced expression of the activity-regulated cytoskeleton protein. Furthermore, the activation of main olfactory bulb circuitry by pheromone volatiles did not cause any modulation in learning and memorizing non-pheromonal volatiles. Our study thus provides the evidence for associations formed between different sensory modalities facilitating the long-term memory formation relevant to social and reproductive behaviors.

Appeasing Pheromones for the Management of Stress and Aggression during Conservation of Wild Canids: Could the Solution Be Right under Our Nose?

Simple Summary

Many canid species are declining globally. It is important to conserve these species that often serve as important predators within ecosystems. Continued human expansion and the resulting habitat fragmentation necessitate conservation interventions, such as translocation, artificial pack formation, and captive breeding programs. However, chronic stress often occurs during these actions, and can result in aggression, and the physiological suppression of immunity and reproduction. Limited options are currently available for stress and aggression management in wild canids. Pheromones provide a promising natural alternative for stress management; an appeasing pheromone has been identified for multiple domestic species and may reduce stress and aggression behaviours. Many pheromones are species-specific, and the appeasing pheromone has been found to have slight compositional changes across species. In this review, the benefits of a dog appeasing pheromone and the need to investigate species-specific derivatives to produce more pronounced and beneficial behavioural and physiological modulation in target species as a conservation tool are examined.

Abstract

Thirty-six species of canid exist globally, two are classified as critically endangered, three as endangered, and five as near threatened. Human expansion and the coinciding habitat fragmentation necessitate conservation interventions to mitigate concurrent population deterioration. The current conservation management of wild canids includes animal translocation and artificial pack formation. These actions often cause chronic stress, leading to increased aggression and the suppression of the immune and reproductive systems. Castration and pharmaceutical treatments are currently used to reduce stress and aggression in domestic and captive canids. The undesirable side effects make such treatments inadvisable during conservation management of wild canids. Pheromones are naturally occurring chemical messages that modulate behaviour between conspecifics; as such, they offer a natural alternative for behaviour modification. Animals are able to distinguish between pheromones of closely related species through small compositional differences but are more likely to have greater responses to pheromones from individuals of the same species. Appeasing pheromones have been found to reduce stress- and aggression-related behaviours in domestic species, including dogs. Preliminary evidence suggests that dog appeasing pheromones (DAP) may be effective in wild canids. However, the identification and testing of species-specific derivatives could produce more pronounced and beneficial behavioural and physiological changes in target species. In turn, this could provide a valuable tool to improve the conservation management of many endangered wild canids.

[Precocious puberty and neuropilin-1 signaling in GnRH neurons]

The survival of the species depends on two closely interlinked processes: the correct functioning of the reproductive system, and the balance between the energy needs of an individual and the supply of energy sources through feeding. These two processes are regulated in the hypothalamus, which produces neurohormones that control various physiological functions. Among these neurohormones, GnRH controls not only the maturation and function of the reproductive organs, including the ovaries and the testes, during puberty and in adulthood, but also sexual attraction. Recent evidence suggest that neuropilin-1-mediated signaling in GnRH-synthesizing neurons could be a linchpin that holds together various neuroanatomical, physiological and behavioral adaptations involved in triggering puberty and achieving reproductive function.

Acquisition of innate odor preference depends on spontaneous and experiential activities during critical period

Animals possess an inborn ability to recognize certain odors to avoid predators, seek food, and find mates. Innate odor preference is thought to be genetically hardwired. Here we report that acquisition of innate odor recognition requires spontaneous neural activity and is influenced by sensory experience during early postnatal development. Genetic silencing of mouse olfactory sensory neurons during the critical period has little impact on odor sensitivity, discrimination, and recognition later in life. However, it abolishes innate odor preference and alters the patterns of activation in brain centers. Exposure to innately recognized odors during the critical period abolishes the associated valence in adulthood in an odor-specific manner. The changes are associated with broadened projection of olfactory sensory neurons and expression of axon guidance molecules. Thus, a delicate balance of neural activity is needed during the critical period in establishing innate odor preference and convergent axon input is required to encode innate odor valence.

The physiological reaction of Siberian hamsters (Phodopus sungorus, Cricetidae) to chemical signals of perspective mating partners before and during courtship

In this investigation we assessed the physiological reaction of hamsters in response to chemical signals from potential sexual partners, and also after a private meeting with them, which allowed us to ascertain the type of mating system for this species. The reception of olfactory signals led to an increase in peroxidase activity in the blood for both sexes, indicative of activity of a non-specific line of immune defense in recipients. The increase in blood cortisol level in response to the chemical signals of a partner was only observed in females. Males spent more time near samples of estrous females, with elevated levels of cortisol in the urine. In olfactory tests, an hour after grouping all the individuals in pairs there was a significant increase in blood peroxidase activity, which indicates the reaction of a non-specific link in the immune system of partners. This increase was greater in the pairs with a mutual preference. Females from these pairs demonstrated a substantial decrease in stress hormone levels in the plasma after an hour of mating in comparison to females prior to mating, and in non-preferred coupling.

Summary: Perception of olfactory signals before and during courtship lead to an increase of non-specific immune activity. For pairs formed by mutual preference there was a noted decrease of stress-hormone only in females.

COVID-19 and Neurological Impairment: Hypothalamic Circuits and Beyond

In December 2019, a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, the capital of Hubei, China. The virus infection, coronavirus disease 2019 (COVID-19), represents a global concern, as almost all countries around the world are affected. Clinical reports have confirmed several neurological manifestations in COVID-19 patients such as headaches, vomiting, and nausea, indicating the involvement of the central nervous system (CNS) and peripheral nervous system (PNS). Neuroinvasion of coronaviruses is not a new phenomenon, as it has been demonstrated by previous autopsies of severe acute respiratory syndrome coronavirus (SARS-CoV) patients who experienced similar neurologic symptoms. The hypothalamus is a complex structure that is composed of many nuclei and diverse neuronal cell groups. It is characterized by intricate intrahypothalamic circuits that orchestrate a finely tuned communication within the CNS and with the PNS. Hypothalamic circuits are critical for maintaining homeostatic challenges including immune responses to viral infections. The present article reviews the possible routes and mechanisms of neuroinvasion of SARS-CoV-2, with a specific focus on the role of the hypothalamic circuits in mediating the neurological symptoms noted during COVID-19 infection.

Encoding innately recognized odors via a generalized population code

Odors carrying intrinsic values often trigger instinctive aversive or attractive responses. It is not known how innate valence is encoded. An intuitive model suggests that the information is conveyed through specific channels in hardwired circuits along the olfactory pathway, insulated from influences of other odors, to trigger innate responses. Here, we show that in mice, mixing innately aversive or attractive odors with a neutral odor and, surprisingly, mixing two odors with the same valence, abolish the innate behavioral responses. Recordings from the olfactory bulb indicate that odors are not masked at the level of peripheral activation and glomeruli independently encode components in the mixture. In contrast, crosstalk among the mitral and tufted (M/T) cells changes their patterns of activity such that those elicited by the mixtures can no longer be linearly decoded as separate components. The changes in behavioral and M/T cell responses are associated with reduced activation of brain areas linked to odor preferences. Thus, crosstalk among odor channels at the earliest processing stage in the olfactory pathway leads to re-coding of odor identity to abolish valence associated with the odors. These results are inconsistent with insulated labeled lines and support a model of a common mechanism of odor recognition for both innate and learned valence associations.

Fish as a model in social neuroscience: conservation and diversity in the social brain network

Mechanisms for fish social behaviours involve a social brain network (SBN) which is evolutionarily conserved among vertebrates. However, considerable diversity is observed in the actual behaviour patterns amongst nearly 30000 fish species. The huge variation found in socio-sexual behaviours and strategies is likely generated by a morphologically and genetically well-conserved small forebrain system. Hence, teleost fish provide a useful model to study the fundamental mechanisms underlying social brain functions. Herein we review the foundations underlying fish social behaviours including sensory, hormonal, molecular and neuroanatomical features. Gonadotropin-releasing hormone neurons clearly play important roles, but the participation of vasotocin and isotocin is also highlighted. Genetic investigations of developing fish brain have revealed the molecular complexity of neural development of the SBN. In addition to straightforward social behaviours such as sex and aggression, new experiments have revealed higher order and unique phenomena such as social eavesdropping and social buffering in fish. Finally, observations interpreted as 'collective cognition' in fish can likely be explained by careful observation of sensory determinants and analyses using the dynamics of quantitative scaling. Understanding of the functions of the SBN in fish provide clues for understanding the origin and evolution of higher social functions in vertebrates.

Coding of pheromones by vomeronasal receptors

Communication between individuals is critical for species survival, reproduction, and expansion. Most terrestrial species, with the exception of humans who predominantly use vision and phonation to create their social network, rely on the detection and decoding of olfactory signals, which are widely known as pheromones. These chemosensory cues originate from bodily fluids, causing attractive or avoidance behaviors in subjects of the same species. Intraspecific pheromone signaling is then crucial to identify sex, social ranking, individuality, and health status, thus establishing hierarchies and finalizing the most efficient reproductive strategies. Indeed, all these features require fine tuning of the olfactory systems to detect molecules containing this information. To cope with this complexity of signals, tetrapods have developed dedicated olfactory subsystems that refer to distinct peripheral sensory detectors, called the main olfactory and the vomeronasal organ, and two minor structures, namely the septal organ of Masera and the Grueneberg ganglion. Among these, the vomeronasal organ plays the most remarkable role in pheromone coding by mediating several behavioral outcomes that are critical for species conservation and amplification. In rodents, this organ is organized into two segregated neuronal subsets that express different receptor families. To some extent, this dichotomic organization is preserved in higher projection areas of the central nervous system, suggesting, at first glance, distinct functions for these two neuronal pathways. Here, I will specifically focus on this issue and discuss the role of vomeronasal receptors in mediating important innate behavioral effects through the recognition of pheromones and other biological chemosignals.

Processing of intraspecific chemical signals in the rodent brain

In the rodent brain, the central processing of ecologically relevant chemical stimuli involves many different areas located at various levels within the neuraxis: the main and accessory olfactory bulbs, some nuclei in the amygdala, the hypothalamus, and brainstem. These areas allow the integration of the chemosensory stimuli with other sensory information and the selection of the appropriate neurohormonal and behavioral response. This review is a brief introduction to the processing of intraspecific chemosensory stimuli beyond the secondary projection, focusing on the activity of the relevant amygdala and hypothalamic nuclei, namely the medial amygdala and ventromedial hypothalamus. These areas are involved in the appropriate interpretation of chemosensory information and drive the selection of the proper response, which may be behavioral or hormonal and may affect the neural activity of other areas in the telencephalon and brainstem.Recent data support the notion that the processing of intraspecific chemical signals is not unique to one chemosensory system and some molecules may activate both the main and the accessory olfactory system. Moreover, both these systems have mixed projections and cooperate for the correct identification of the stimuli and selection of relevant responses.

Pheromone effects on the human hypothalamus in relation to sexual orientation and gender

Pheromones are chemicals that serve communicational purposes within a species. In most terrestrial mammals, pheromones are detected by either the olfactory epithelium or the vomeronasal organ and processed by various downstream structures including the medial amygdala and the hypothalamus to regulate motivated behaviors and endocrine responses. The search for human pheromones began in the 1970s. Whereas bioactive ligands are yet to be identified, there has been accumulating evidence that human body odors exert a range of pheromone-like effects on the recipients, including triggering innate behavioral responses, modulating endocrine levels, signaling social information, and affecting mood and cognition. In parallel, results from recent brain imaging studies suggest that body odors evoke distinct neural responses from those observed with common nonsocial odors. Two endogenous steroids androsta-4,16,- dien-3-one and estra-1,3,5(10),16-tetraen-3-ol are considered by some as candidates for human sex pheromones. The two substances produce sexually dimorphic effects on human perception, mood, and physiological arousal. Moreover, they reportedly elicit different hypothalamic response patterns in manners contingent on the recipients' sex and sexual orientation. Neuroendocrine mechanisms underlying the effects of human chemosignals are not yet clear and await future detailed analyses.

GnRH neurogenesis depends on embryonic pheromone receptor expression

Gonadotropin-releasing hormone (GnRH) neurons control mammalian reproduction and migrate from their birthplace in the nasal placode to the hypothalamus during development. Despite much work on the origin and migration of GnRH neurons, the processes that control GnRH lineage formation are not fully understood. Here, we demonstrate that Nhlh genes control vomeronasal receptor expression in the developing murine olfactory placode associated with the generation of the first GnRH neurons at embryonic days (E)10-12. Inactivation of ß2-microglobulin (ß2-m), which selectively affects surface expression of V2Rs, dramatically decreased the number of GnRH neurons in the Nhlh2 mutant background, preventing rescue of fertility in female Nhlh2 mutant mice by male pheromones. In addition, we show that GnRH neurons generated after E12 fail to establish synaptic connections to the vomeronasal amygdala, suggesting the existence of functionally specialized subpopulations of GnRH neurons, which process pheromonal information.

HPG-Dependent Peri-Pubertal Regulation of Adult Neurogenesis in Mice

Adult neurogenesis, a striking form of neural plasticity, is involved in the modulation of social stimuli driving reproduction. Previous studies on adult neurogenesis have shown that this process is significantly modulated around puberty in female mice. Puberty is a critical developmental period triggered by increased secretion of the gonadotropin releasing hormone (GnRH), which controls the activity of the hypothalamic-pituitary-gonadal axis (HPG). Secretion of HPG-axis factors at puberty participates to the refinement of neural circuits that govern reproduction. Here, by exploiting a transgenic GnRH deficient mouse model, that progressively loses GnRH expression during postnatal development (GnRH::Cre;Dicer ^loxP/loxP mice), we found that a postnatally-acquired dysfunction in the GnRH system affects adult neurogenesis selectively in the subventricular-zone neurogenic niche in a sexually dimorphic way. Moreover, by examining adult females ovariectomized before the onset of puberty, we provide important evidence that, among the HPG-axis secreting factors, the circulating levels of gonadal hormones during pre-/peri-pubertal life contribute to set-up the proper adult subventricular zone-olfactory bulb neurogenic system.

Neuropilin-1 expression in GnRH neurons regulates prepubertal weight gain and sexual attraction

Hypothalamic neurons expressing gonadotropin-releasing hormone (GnRH), the "master molecule" regulating reproduction and fertility, migrate from their birthplace in the nose to their destination using a system of guidance cues, which include the semaphorins and their receptors, the neuropilins and plexins, among others. Here, we show that selectively deleting neuropilin-1 in new GnRH neurons enhances their survival and migration, resulting in excess neurons in the hypothalamus and in their unusual accumulation in the accessory olfactory bulb, as well as an acceleration of mature patterns of activity. In female mice, these alterations result in early prepubertal weight gain, premature attraction to male odors, and precocious puberty. Our findings suggest that rather than being influenced by peripheral energy state, GnRH neurons themselves, through neuropilin-semaphorin signaling, might engineer the timing of puberty by regulating peripheral adiposity and behavioral switches, thus acting as a bridge between the reproductive and metabolic axes.

Unexplained repeated pregnancy loss is associated with altered perceptual and brain responses to men's body-odor

Mammalian olfaction and reproduction are tightly linked, a link less explored in humans. Here, we asked whether human unexplained repeated pregnancy loss (uRPL) is associated with altered olfaction, and particularly altered olfactory responses to body-odor. We found that whereas most women with uRPL could identify the body-odor of their spouse, most control women could not. Moreover, women with uRPL rated the perceptual attributes of men's body-odor differently from controls. These pronounced differences were accompanied by an only modest albeit significant advantage in ordinary, non-body-odor-related olfaction in uRPL. Next, using structural and functional brain imaging, we found that in comparison to controls, most women with uRPL had smaller olfactory bulbs, yet increased hypothalamic response in association with men's body-odor. These findings combine to suggest altered olfactory perceptual and brain responses in women experiencing uRPL, particularly in relation to men's body-odor. Whether this link has any causal aspects to it remains to be explored.

[Use of Transsynaptic Viral Tracers for Observing Neural Circuit Control of Physiological Responses]

Central neural circuits in the brain receive and integrate environmental and internal information to enable the animals to execute appropriate behaviors and physiological responses. Communication between the brain and peripheral organs via peripheral neural circuits maintains energy homeostasis in the body. Therefore it is important to investigate the anatomical organization of central and peripheral neural circuits for elucidating the mechanisms of energy homeostasis. Transsynaptic viral tracers can travel through connected neurons via synaptic connections and have been used to delineate the anatomical organization of neural circuits with specific functions. Herein, I review our recent studies investigating neural circuits and their involvement in physiological changes using transsynaptic tracers.

Population Density Modulates the Duration of Reproduction of C. elegans

Population density can modulate the developmental trajectory of Caenorhabditis elegans larvae by promoting entry into dauer diapause, which is characterized by metabolic and anatomical remodeling and stress resistance [1, 2]. Genetic analysis of dauer formation has identified the involvement of evolutionarily conserved endocrine signaling pathways, including the DAF-2/insulin-like receptor signaling pathway [3-7]. Chemical and metabolomic analysis of dauer-inducing pheromone has identified a family of small molecules, ascarosides, which act potently to communicate increased population density and promote dauer formation [1, 8-10]. Here, we show that adult animals respond to ascarosides produced under conditions of increased population density by increasing the duration of reproduction. We observe that the ascarosides that promote dauer entry of larvae also act on adult animals to attenuate expression of the insulin peptide INS-6 from the ASI chemosensory neurons, resulting in diminished neuroendocrine insulin signaling that extends the duration of reproduction. Genetic analysis of ins-6 and corresponding insulin-signaling pathway mutants showed that the effect of increased population density on reproductive span was mimicked by ins-6 loss of function that exerted effects on duration of reproduction through the canonical DAF-2-DAF-16 pathway. We further observed that the effect of population density on reproductive span acted through DAF-16-dependent and DAF-16-independent pathways upstream of DAF-12, paralleling in adults what has been observed for the dauer developmental decision of larvae. Our data suggest that, under conditions of increased population density, C. elegans animals prolong the duration of reproductive egg laying, which may enable the subsequent development of progeny under more favorable conditions.

The Effects of Essential Oils and Terpenes in Relation to Their Routes of Intake and Application

Essential oils have been used in multiple ways, i.e., inhaling, topically applying on the skin, and drinking. Thus, there are three major routes of intake or application involved: the olfactory system, the skin, and the gastro-intestinal system. Understanding these routes is important for clarifying the mechanisms of action of essential oils. Here we summarize the three systems involved, and the effects of essential oils and their constituents at the cellular and systems level. Many factors affect the rate of uptake of each chemical constituent included in essential oils. It is important to determine how much of each constituent is included in an essential oil and to use single chemical compounds to precisely test their effects. Studies have shown synergistic influences of the constituents, which affect the mechanisms of action of the essential oil constituents. For the skin and digestive system, the chemical components of essential oils can directly activate gamma aminobutyric acid (GABA) receptors and transient receptor potential channels (TRP) channels, whereas in the olfactory system, chemical components activate olfactory receptors. Here, GABA receptors and TRP channels could play a role, mostly when the signals are transferred to the olfactory bulb and the brain.

[Modern studies of the role of the vomeronasal system in the perception of pheromones and their impact on social and sexual behavior]

The vomeronasal system (VNS) provides regulation of a wide range of autonomic and affective functions, behavioral reactions in response to the specific chemical stimuli pheromones secreted by mammals, including humans. The results of experimental studies confirming the existence of VNS and explaining the basic mechanisms of its functioning are presented. The results of studies of healthy volunteers, explaining the effect of pheromones on a number of functions of the human body, are considered.

More than reproduction: Central gonadotropin-releasing hormone antagonism decreases maternal aggression in lactating rats

Gonadotropin-releasing hormone (GnRH) is a major regulator and activator of the hypothalamic-pituitary-gonadal axis. Many studies have demonstrated the importance of GnRH in reproduction and sexual behaviour. However, to date, only a single study shows an involvement of GnRH in maternal behaviour where a 30% reduction of GnRH neurones abolishes a mother's motivation to retrieve pups. On this basis, we aimed to investigate the effects of acute central GnRH receptor blockade in lactating rats on maternal care under non-stress and stress conditions, maternal motivation in the pup retrieval test, maternal anxiety on the elevated plus maze, and maternal aggression in the maternal defence test. We found that acute central infusion of a GnRH antagonist ([d-Phe^2,6 ,Pro³ ]-luteinising hormone-releasing hormone; 0.5 ng 5 μL^-1 ) impaired a mother's attack behaviour against a female intruder rat during the maternal defence test compared to vehicle controls. However, in contrast to the previous study on reduced GnRH neurones, acute central GnRH antagonism did not affect pup retrieval, nor any other parameter of maternal behaviour or maternal anxiety. Taken together, GnRH receptor activation is mandatory for protection of the offspring. These findings shed new light on GnRH as a neuropeptide acting not exclusively on the reproductive axis but, additionally, on maternal behaviour including pup retrieval and maternal aggression.

Expansion of vomeronasal receptor genes (OlfC) in the evolution of fright reaction in Ostariophysan fishes

Ostariophysans are the most diverse group of freshwater fishes and feature a pheromone-elicited fright reaction. However, the genetic basis of fright reaction is unclear. Here, we compared vomeronasal type 2 receptor-like (OlfC) genes from fishes having and lacking fright reaction, to provide insight into evolution of pheromonal olfaction in fishes. We found OlfC genes expanded remarkably in ostariophysans having fright reaction compared with fishes lacking fright reaction. Phylogenetic analysis indicates OlfC subfamily 9 expanded specifically in ostariophysans having fright reaction. Principle component and phylogenetic logistic regression analysis partitioned fishes by ecotype (having or lacking fright reaction) and identified OlfC subfamily 9 as being an important factor for fright reaction. Expression levels of expanded OlfC subfamily genes after fright reaction in zebrafish changed more than did genes that had not expanded. Furthermore, evidence of positive selection was found in the expanded OlfC proteins in ostariophysan fishes having fright reaction. These results provide new insight into the genetic basis of fright reaction in ostariophysan fish and will enable future research into the mechanism of action of OlfC proteins.

The Relationship Between Progesterone, Sleep, and LH and FSH Secretory Dynamics in Early Postmenarchal Girls

CONTEXT

During puberty, LH pulse frequency increases during sleep; in women, LH pulse frequency slows during sleep in the early/middle follicular phase (FP) of the menstrual cycle. The origin and significance of this developmental transition are unknown.

OBJECTIVE

To determine the relationship between progesterone (P4) exposure, sleep-related slowing of LH pulses in the FP, and the intercycle FSH rise, which promotes folliculogenesis, in early postmenarchal girls.

METHODS

23 girls (gynecologic age 0.4 to 3.5 years) underwent hormone measurements and pelvic ultrasounds during two consecutive cycles and one frequent blood sampling study with concurrent polysomnography during the FP.

RESULTS

Subjects demonstrated one of four patterns during cycle 1 that represent a continuum of P4 exposure: ovulatory cycles with normal or short luteal phase lengths or anovulatory cycles ± follicle luteinization. Peak serum P4 and urine pregnanediol (Pd) in cycle 1 were inversely correlated with LH pulse frequency during sleep in the FP of cycle 2 (r = -0.5; P = 0.02 for both). The intercycle FSH rise and folliculogenesis in cycle 2 were maintained after anovulatory cycles without P4 or Pd exposure or nocturnal slowing of LH pulse frequency in the FP.

CONCLUSIONS

During late puberty, rising P4 levels from follicle luteinization and ovulation may promote a slower LH pulse frequency during sleep in the FP. However, a normal FSH rise and follicle growth can occur in the absence of P4-associated slowing. These studies therefore suggest that an immature LH secretory pattern during sleep is unlikely to contribute to menstrual irregularity in the early postmenarchal years.

Neuroanatomical Framework of the Metabolic Control of Reproduction

A minimum amount of energy is required for basic physiological processes, such as protein biosynthesis, thermoregulation, locomotion, cardiovascular function, and digestion. However, for reproductive function and survival of the species, extra energy stores are necessary. Production of sex hormones and gametes, pubertal development, pregnancy, lactation, and parental care all require energy reserves. Thus the physiological systems that control energy homeostasis and reproductive function coevolved in mammals to support both individual health and species subsistence. In this review, we aim to gather scientific knowledge produced by laboratories around the world on the role of the brain in integrating metabolism and reproduction. We describe essential neuronal networks, highlighting key nodes and potential downstream targets. Novel animal models and genetic tools have produced substantial advances, but critical gaps remain. In times of soaring worldwide obesity and metabolic dysfunction, understanding the mechanisms by which metabolic stress alters reproductive physiology has become crucial for human health.

Molecular, spatial, and functional single-cell profiling of the hypothalamic preoptic region

The hypothalamus controls essential social behaviors and homeostatic functions. However, the cellular architecture of hypothalamic nuclei-including the molecular identity, spatial organization, and function of distinct cell types-is poorly understood. Here, we developed an imaging-based in situ cell-type identification and mapping method and combined it with single-cell RNA-sequencing to create a molecularly annotated and spatially resolved cell atlas of the mouse hypothalamic preoptic region. We profiled ~1 million cells, identified ~70 neuronal populations characterized by distinct neuromodulatory signatures and spatial organizations, and defined specific neuronal populations activated during social behaviors in male and female mice, providing a high-resolution framework for mechanistic investigation of behavior circuits. The approach described opens a new avenue for the construction of cell atlases in diverse tissues and organisms.

Neurogenesis and sexual behavior

Different conditions induce proliferation, migration and integration of new neurons in the adult brain. This process of neurogenesis is a clear example of long lasting plastic changes in the brain of different species. Sexual behavior is a motivated behavior that is crucial for the survival of the species, but an individual can spend all his life without displaying sexual behavior. In the present review, we briefly describe some of the effects of pheromones on neurogenesis. We review in detail studies describing the effects of sexual behavior in both males and females on proliferation, migration and integration of new cells and neurons. It will become evident that most of the studies have been done in rodents, assessing the effects of this behavior on neurogenesis within the dentate gyrus of the hippocampus and in the subventricular zone - rostral migratory stream - olfactory bulb system.

Female sexual behavior in mice is controlled by kisspeptin neurons

Sexual behavior is essential for the survival of many species. In female rodents, mate preference and copulatory behavior depend on pheromones and are synchronized with ovulation to ensure reproductive success. The neural circuits driving this orchestration in the brain have, however, remained elusive. Here, we demonstrate that neurons controlling ovulation in the mammalian brain are at the core of a branching neural circuit governing both mate preference and copulatory behavior. We show that male odors detected in the vomeronasal organ activate kisspeptin neurons in female mice. Classical kisspeptin/Kiss1R signaling subsequently triggers olfactory-driven mate preference. In contrast, copulatory behavior is elicited by kisspeptin neurons in a parallel circuit independent of Kiss1R involving nitric oxide signaling. Consistent with this, we find that kisspeptin neurons impinge onto nitric oxide-synthesizing neurons in the ventromedial hypothalamus. Our data establish kisspeptin neurons as a central regulatory hub orchestrating sexual behavior in the female mouse brain.

Mate preference and copulatory behavior in female rodents are coordinated with the ovulation cycles of the animal. This study shows that hypothalamic kisspeptin neurons control both mate choice and copulation, and therefore, that sexual behavior and ovulation may be synchronized by the same neuropeptide.

Olfaction and Pheromones: Uncanonical Sensory Influences and Bulbar Interactions

The rodent main and accessory olfactory systems (AOS) are considered functionally and anatomically segregated information-processing pathways. Each system is devoted to the detection of volatile odorants and pheromones, respectively. However, a growing number of evidences supports a cooperative interaction between them. For instance, at least four non-canonical receptor families (i.e., different from olfactory and vomeronasal receptor families) have been recently discovered. These atypical receptor families are expressed in the sensory organs of the nasal cavity and furnish parallel processing-pathways that detect specific stimuli and mediate specific behaviors as well. Aside from the receptor and functional diversity of these sensory modalities, they converge into a poorly understood bulbar area at the intersection of the main- main olfactory bulb (MOB) and accessory olfactory bulb (AOB) that has been termed olfactory limbus (OL). Given the intimate association the OL with specialized glomeruli (i.e., necklace and modified glomeruli) receiving uncanonical sensory afferences and its interactions with the MOB and AOB, the possibility that OL is a site of non-olfactory and atypical vomeronasal sensory decoding is discussed.

The Two Populations of Kisspeptin Neurons Are Involved in the Ram-Induced LH Pulsatile Secretion and LH Surge in Anestrous Ewes

Exposure to a ram during spring stimulates luteinizing hormone (LH) secretion and can induce ovulation in sexually quiescent ewes ("ram effect"). Kisspeptin (Kiss) present in the arcuate nucleus (ARC) and the preoptic area (POA) is a potent stimulators of LH secretion. Our aim was to investigate whether Kiss neurons mediate the increase in LH secretion during the ram effect. With double immunofluorescent detection, we identified Kiss neurons (Kiss IR) activated (Fos IR) by exposure to a ram for 2 hours (M2) or 12 hours (M12) or to ewes for 2 hours (C). The density of cells Kiss + Fos IR and the proportion of Kiss IR cells that were also Fos IR cells were higher in M2 and M12 than in C in ARC (P < 0.002) and POA (P < 0.02). In ARC, these parameters were also higher in M12 than in M2 (P < 0.02 and P < 0.05). Kiss antagonist (P234 10-6M) administered by retrodialysis in POA for 3 hours at the time of introduction of the ram reduced the amplitude of the male-induced increase in LH concentration compared with solvent (P < 0.02). In ARC, P234 had a more limited effect (P < 0.038 1 hour after P234) but pulse frequency increased less than after solvent (P = 0.07). In contrast, Kiss antagonist (P271 10-4M) infused in ARC but not POA 6 to 18 hours after introduction of the ram prevented the LH surge in the ewe (0/6 vs 4/5 and 4/6 in C). These results suggest that both populations of Kiss neurons are involved in the ram-induced pulsatile LH secretion and in the LH surge.