Search Results (18)

The vomeronasal system (VNS) is directly linked to the various behavior and ecology of all animal species, and understanding it might help to prevent deer damage. We therefore histochemically analyzed the accessory olfactory bulb (AOB) and the vomeronasal organ (VNO) that, respectively, function as a primary integrative center and a peripheral receptor organ, in Hokkaido sika deer (Cervus nippon ssp. yesoensis). The AOB consisted of the vomeronasal nerve, glomerular, plexiform, and granule cell layers. We found that G protein α subunit i2 (Gαi2) and o (Gαo) that are, respectively, coupled with vomeronasal receptor type 1 and 2 families were strongly and weakly expressed in the glomerular layer, respectively. These properties of the AOB of sika deer were similar to those of other artiodactyl species, including wapiti. We then explored the sika deer VNO using 21 lectins that bind to each glycan structure. Although various cell types in the VNO had unique lectin binding profiles, all 21 lectins bound to the free border of the sensory epithelium, suggesting that various glycoconjugates are involved in pheromone detection in sika deer via the VNO. Furthermore, the reactivity of some lectins in the sensory epithelium and vomeronasal gland differed from those of roe deer and wapiti. Our findings suggest that the composition of glycoconjugates in the VNO differs among deer species. Full article

Over the last three decades, adult neurogenesis in mammals has been a central focus of neurobiological research, providing insights into brain plasticity and function. However, interest in this field has recently waned due to challenges in translating findings into regenerative applications and the ongoing debate about the persistence of this phenomenon in the adult human brain. Despite these hurdles, significant progress has been made in understanding how adult neurogenesis plays a critical role in the adaptation of brain circuits to environmental stimuli regulating key brain functions. This review focuses on the role of olfactory neurogenesis in the brain’s response to social reproductive cues in rodents, highlighting its influence on animal behaviors critical for survival. We also address open questions and propose future directions to advance our understanding of the relationship between adult neurogenesis and reproductive function regulation. Full article

Olfactory sensitivity to odorant molecules is a complex biological function influenced by both endogenous factors, such as genetic background and physiological state, and exogenous factors, such as environmental conditions. In animals, this vital ability is mediated by olfactory sensory neurons (OSNs), which are distributed across several specialized olfactory subsystems depending on the species. Using the phosphorylation of the ribosomal protein S6 (rpS6) in OSNs following sensory stimulation, we developed an ex vivo assay allowing the simultaneous conditioning and odorant stimulation of different mouse olfactory subsystems, including the main olfactory epithelium, the vomeronasal organ, and the Grueneberg ganglion. This approach enabled us to observe odorant-induced neuronal activity within the different olfactory subsystems and to demonstrate the impact of environmental conditioning, such as temperature variations, on olfactory sensitivity, specifically in the Grueneberg ganglion. We further applied our rpS6-based assay to the human olfactory system and demonstrated its feasibility. Our findings show that analyzing rpS6 signal intensity is a robust and highly reproducible indicator of neuronal activity across various olfactory systems, while avoiding stress and some experimental limitations associated with in vivo exposure. The potential extension of this assay to other conditioning paradigms and olfactory systems, as well as its application to other animal species, including human olfactory diagnostics, is also discussed. Full article

The accessory olfactory bulb (AOB) processes chemical signals crucial for species-specific socio-sexual behaviors. There is limited information about the AOB of wild rodents, and this study aims to characterize the neurochemical organization of the AOB in the fossorial water vole (Arvicola scherman), a subterranean Cricetidae rodent. We employed histological, immunohistochemical, and lectin-histochemical techniques. The AOB of these voles exhibits a distinct laminar organization, with prominent mitral cells and a dense population of periglomerular cells. Lectin histochemistry and G-protein immunohistochemistry confirmed the existence of an antero-posterior zonation. Immunohistochemical analysis demonstrated significant expression of PGP 9.5, suggesting its involvement in maintaining neuronal activity within the AOB. In contrast, the absence of SMI-32 labelling in the AOB, compared to its strong expression in the main olfactory bulb, highlights functional distinctions between these two olfactory subsystems. Calcium-binding proteins allowed the characterization of atypical sub-bulbar nuclei topographically related to the AOB. All these features suggest that the AOB of Arvicola scherman is adapted for enhanced processing of chemosensory signals, which may play a pivotal role in its subterranean lifestyle. Our results provide a foundation for future studies exploring the implications of these adaptations, including potential improvements in the management of these vole populations. Full article

The mammalian vomeronasal system enables the perception of chemical signals crucial for social communication via the receptor families V1R and V2R. These receptors are linked with the G-protein subunits, Gαi2 and Gαo, respectively. Exploring the evolutionary pathways of V1Rs and V2Rs across mammalian species remains a significant challenge, particularly when comparing genomic data with emerging immunohistochemical evidence. Recent studies have revealed the expression of Gαo in the vomeronasal neuroepithelium of wild canids, including wolves and foxes, contradicting predictions based on current genomic annotations. Our study provides detailed immunohistochemical evidence, mapping the expression of V2R receptors in the vomeronasal sensory epithelium, focusing particularly on wild canids, specifically wolves and foxes. An additional objective involves contrasting these findings with those from domestic species like dogs to highlight the evolutionary impacts of domestication on sensory systems. The employment of a specific antibody raised against the mouse V2R2, a member of the C-family of vomeronasal receptors, V2Rs, has confirmed the presence of V2R2-immunoreactivity (V2R2-ir) in the fox and wolf, but it has revealed the lack of expression in the dog. This may reflect the impact of domestication on the regression of the VNS in this species, in contrast to their wild counterparts, and it underscores the effects of artificial selection on sensory functions. Thus, these findings suggest a more refined chemical detection capability in wild species. Full article

This review addresses the role of chemical communication in mammals, giving special attention to the vomeronasal system in pheromone-mediated interactions. The vomeronasal system influences many social and sexual behaviors, from reproduction to species recognition. Interestingly, this system shows greater evolutionary variability compared to the olfactory system, emphasizing its complex nature and the need for thorough research. The discussion starts with foundational concepts of chemocommunication, progressing to a detailed exploration of olfactory systems. The neuroanatomy of the vomeronasal system stands in contrast with that of the olfactory system. Further, the sensory part of the vomeronasal system, known as the vomeronasal organ, and the integration center of this information, called the accessory olfactory bulb, receive comprehensive coverage. Secondary projections of both the olfactory and vomeronasal systems receive attention, especially in relation to the dual olfactory hypothesis. The review concludes by examining the organization of the vomeronasal system in four distinct mammalian groups: rodents, marsupials, herpestids, and bovids. The aim is to highlight the unique morphofunctional differences resulting from the adaptive changes each group experienced. Full article

Gonadotropin-releasing hormone (GnRH) neurons are key neuroendocrine cells in the brain as they control reproduction by regulating hypothalamic-pituitary-gonadal axis function. In this context, anti-Müllerian hormone (AMH), growth hormone (GH), and insulin-like growth factor 1 (IGF1) were shown to improve GnRH neuron migration and function in vitro. Whether AMH, GH, and IGF1 signaling pathways participate in the development and function of GnRH neurons in vivo is, however, currently still unknown. To assess the role of AMH, GH, and IGF1 systems in the development of GnRH neuron, we evaluated the expression of AMH receptors (AMHR2), GH (GHR), and IGF1 (IGF1R) on sections of ex vivo mice at different development stages. The expression of AMHR2, GHR, and IGF1R was assessed by immunofluorescence using established protocols and commercial antibodies. The head sections of mice were analyzed at E12.5, E14.5, and E18.5. In particular, at E12.5, we focused on the neurogenic epithelium of the vomeronasal organ (VNO), where GnRH neurons, migratory mass cells, and the pioneering vomeronasal axon give rise. At E14.5, we focused on the VNO and nasal forebrain junction (NFJ), the two regions where GnRH neurons originate and migrate to the hypothalamus, respectively. At E18.5, the median eminence, which is the hypothalamic area where GnRH is released, was analyzed. At E12.5, double staining for the neuronal marker ß-tubulin III and AMHR2, GHR, or IGF1R revealed a signal in the neurogenic niches of the olfactory and VNO during early embryo development. Furthermore, IGF1R and GHR were expressed by VNO-emerging GnRH neurons. At E14.5, a similar expression pattern was found for the neuronal marker ß-tubulin III, while the expression of IGF1R and GHR began to decline, as also observed at E18.5. Of note, hypothalamic GnRH neurons labeled for PLXND1 tested positive for AMHR2 expression. Ex vivo experiments on mouse sections revealed differential protein expression patterns for AMHR2, GHR, and IGF1R at any time point in development between neurogenic areas and hypothalamic compartments. These findings suggest a differential functional role of related systems in the development of GnRH neurons. Full article

In numerous animals, one essential chemosensory organ that detects chemical signals is the vomeronasal organ (VNO), which is involved in species-specific behaviors, including social and sexual behaviors. The purpose of this study is to investigate the mechanism underlying the processing of chemosensory cues in semi-aquatic mammals using muskrats as the animal model. Muskrat (Ondatra zibethicus) has a sensitive VNO system that activates seasonal breeding behaviors through receiving specific substances, including pheromones and hormones. Vomeronasal organ receptor type 1 (V1R) and type 2 (V2R) and estrogen receptor α and β (ERα and ERβ) were found in sensory epithelial cells, non-sensory epithelial cells and lamina propria cells of the female muskrats’ VNO. V2R and ERα mRNA levels in the VNO during the breeding period declined sharply, in comparison to those during the non-breeding period, while V1R and ERβ mRNA levels were detected reversely. Additionally, transcriptomic study in the VNO identified that differently expressed genes might be related to estrogen signal and metabolic pathways. These findings suggested that the seasonal structural and functional changes in the VNO of female muskrats with different reproductive status and estrogen was regulated through binding to ERα and ERβ in the female muskrats’ VNO. Full article

Chemical communication in mammals is ensured by exchanging chemical signals through the vomeronasal organ (VNO) and its ability to detect pheromones. The alteration of this organ has been proven to impact animal life, participating in the onset of aggressive behaviors in social groups. To date, few studies have highlighted the possible causes leading to these alterations, and the farming environment has not been investigated, even though irritant substances such as ammonia are known to induce serious damage in the respiratory tract. The goal of this study was to investigate the environmental impact on the VNO structure. Thirty mice were split into three groups, one housed in normal laboratory conditions and the other two in confined environments, with or without the release of litter ammonia. VNOs were analyzed using histology and immunohistochemistry to evaluate the effect of different environments on their condition. Both restricted conditions induced VNO alterations (p = 0.0311), soft-tissue alteration (p = 0.0480), and nonsensory epithelium inflammation (p = 0.0024). There was glycogen accumulation (p < 0.0001), the olfactory marker protein was underexpressed (p < 0.0001), and Gαi2 positivity remained unchanged while Gαo expression was upregulated in confined conditions. VNO conditions seemed to worsen with ammonia, even if not always significantly. These murine model results suggest that the housing environment can strongly impact VNO conditions, providing novel insights for improving indoor farming systems. Full article

The sense of smell plays a fundamental role in mammalian survival. There is a considerable amount of information available on the vomeronasal system of both domestic and wild canids. However, much less information is available on the canid main olfactory system, particularly at the level of the main olfactory bulb. Comparative study of the neuroanatomy of wild and domestic canids provides an excellent model for understanding the effects of selection pressure associated with domestication. A comprehensive histological (hematoxylin–eosin, Nissl, Tolivia and Gallego’s Trichrome stains), lectin (UEA, LEA) and immunohistochemical (Gαo, Gαi2, calretinin, calbindin, olfactory marker protein, glial fibrillary acidic protein, microtubule-associated protein 2) study of the olfactory bulbs of the dog, fox and wolf was performed. Our study found greater macroscopic development of the olfactory bulb in both the wolf and fox compared to the dog. At the microscopic level, all three species show a well-developed pattern of lamination and cellularity typical of a macrosmatic animal. However, greater development of cellularity in the periglomerular and mitral layers of wild canids is characteristic. Likewise, the immunohistochemical study shows comparable results between the three species, but with a noticeably higher expression of markers in wild canids. These results suggest that the reduction in encephalization experienced in dogs due to domestication also corresponds to a lower degree of morphological and neurochemical differentiation of the olfactory bulb. Full article

We approached the study of the main (MOB) and accessory olfactory bulbs (AOB) of the meerkat (Suricata suricatta) aiming to fill important gaps in knowledge regarding the neuroanatomical basis of olfactory and pheromonal signal processing in this iconic species. Microdissection techniques were used to extract the olfactory bulbs. The samples were subjected to hematoxylin-eosin and Nissl stains, histochemical (Ulex europaeus agglutinin, Lycopersicon esculentum agglutinin) and immunohistochemical labelling (Gαo, Gαi2, calretinin, calbindin, olfactory marker protein, glial fibrillary acidic protein, microtubule-associated protein 2, SMI-32, growth-associated protein 43). Microscopically, the meerkat AOB lamination pattern is more defined than the dog’s, approaching that described in cats, with well-defined glomeruli and a wide mitral-plexiform layer, with scattered main cells and granular cells organized in clusters. The degree of lamination and development of the meerkat MOB suggests a macrosmatic mammalian species. Calcium-binding proteins allow for the discrimination of atypical glomerular subpopulations in the olfactory limbus between the MOB and AOB. Our observations support AOB functionality in the meerkat, indicating chemosensory specialization for the detection of pheromones, as identified by the characterization of the V1R vomeronasal receptor family and the apparent deterioration of the V2R receptor family. Full article

Quiescin Q6 sulfhydryl oxidase 1 (QSOX1) catalyzes the oxidation of the sulfhydryl group to disulfide bond and is widely expressed in various tissues. This study focuses on investigating QSOX1′s spatiotemporal and cellular protein expression profile of the pregnant uterus, placenta, and developing embryo during mouse pregnancy. Immunohistochemical staining was used to reveal the localization of QSOX1 protein, and HistoQuest was applied to quantify protein levels. The expression level of QSOX1 in the decidua and muscle cells of the pregnant uterus fluctuated dramatically during pregnancy. QSOX1 was ubiquitously expressed in the labyrinth, junction zone, and chorionic plate in the placenta. The quantitative analysis found that this protein was highly expressed in the spinal cord, lens, midbrain, cerebellum, medulla oblongata, and tooth of mouse embryos, followed by the heart, intercostal muscle, diaphragm, intermediate zone, extrinsic ocular muscle, spine, pons, epidermis, tongue, ganglion, vomeronasal organ, thoracic vertebrae, and thymus. Interestingly, QSOX1 was also markedly expressed in olfactory system tissues. This comprehensive spatiotemporal study of QSOX1 protein expression will provide a basis for further investigations of the QSOX1 physiological function in the pregnant uterus, placenta, and developing embryo. Full article

Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019, suffer from respiratory and non-respiratory symptoms. Among these symptoms, the loss of smell has attracted considerable attention. The objectives of this study were to determine which cells are infected, what happens in the olfactory system after viral infection, and how these pathologic changes contribute to olfactory loss. For this purpose, Syrian golden hamsters were used. First, we verified the olfactory structures in the nasal cavity of Syrian golden hamsters, namely the main olfactory epithelium, the vomeronasal organ, and their cellular components. Second, we found angiotensin-converting enzyme 2 expression, a receptor protein of SARS-CoV-2, in both structures and infections of supporting, microvillar, and solitary chemosensory cells. Third, we observed pathological changes in the infected epithelium, including reduced thickness of the mucus layer, detached epithelia, indistinct layers of epithelia, infiltration of inflammatory cells, and apoptotic cells in the overall layers. We concluded that a structurally and functionally altered microenvironment influences olfactory function. We observed the regeneration of the damaged epithelium, and found multilayers of basal cells, indicating that they were activated and proliferating to reconstitute the injured epithelium. Full article

In mammalian reproduction, sexually active males seek female conspecifics, while estrous females try to approach males. This sex-specific response tendency is called sexual preference. In small rodents, sexual preference cues are mainly chemosensory signals, including pheromones. In this article, we review the physiological mechanisms involved in sexual preference for opposite-sex chemosensory signals in well-studied laboratory rodents, mice, rats, and hamsters of both sexes, especially an overview of peripheral sensory receptors, and hormonal and central regulation. In the hormonal regulation section, we discuss potential rodent brain bisexuality, as it includes neural substrates controlling both masculine and feminine sexual preferences, i.e., masculine preference for female odors and the opposite. In the central regulation section, we show the substantial circuit regulating sexual preference and also the influence of sexual experience that innate attractants activate in the brain reward system to establish the learned attractant. Finally, we review the regulation of sexual preference by neuropeptides, oxytocin, vasopressin, and kisspeptin. Through this review, we clarified the contradictions and deficiencies in our current knowledge on the neuroendocrine regulation of sexual preference and sought to present problems requiring further study. Full article

The vomeronasal organ (VNO) detects specific chemicals such as pheromones and kairomones. Hedgehogs (Eulipotyphla: Erinaceidae) have a well-developed accessory olfactory bulb that receives projections from the VNO, but little is known about the hedgehog VNO. Here, we studied the histological features of the VNO in five individual African pygmy hedgehogs by hematoxylin-eosin, periodic acid-Schiff, and Alcian blue stains. The hedgehog VNO comprises a hyaline cartilage capsule, soft tissue and epithelial lumen, and it branches from the site just before the incisive duct opening into the nasal cavity. The soft tissues contain several small mucous (or mucoserous) glands and a large serous gland, and many venous sinuses all around the lumen. The VNO lumen is round to oval throughout the hedgehog VNO, and the sensory epithelium lines almost the entire rostral part and medial wall of the middle part. These findings indicate that the VNO is functional and plays an important role in the hedgehog. Notably, the VNO apparently has a characteristic flushing mechanism with serous secretions like those of gustatory glands, which the hedgehog might frequently use to recognize the external environment. Full article