Vomeronasal Organ

The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don t know either if, or how, visual cues might have direct and developmental effects on hormone levels in other people, the biological basis for the development of visually perceived human physical attraction is currently somewhat questionable. In contrast, the biological basis for the development of physical attraction based on chemical signals is well detailed.

The buller steer syndrome is found among confined and pasture-kept cattle. The buller behavior occurs when a steer is repeatedly mounted (“buller”) and ridden by its pen mates (“rider”) until it is injured or killed. The usual practice is to remove the animal being ridden. The ridden animals are typically grouped together in a “buller” pen where little or no

Tongue-flicking is a sensory-gathering behavior used by snakes to deliver odorants to the vomeronasal organ. In the present study we provide a detailed description of environmental control and motor patterns of tongue-flicking in garter snakes, Thamnophis sirtalis. Tongue-flicks were monitored during prey extract trailing, foraging, delivery of air-borne odors and in an open field. Tongue-flick rates increased during airborne odor delivery and as a function of prey extract concentration during trailing, as previously reported. Motivation and prey consumption appeared to modify tongue-flick patterns since 1. tongue-flick rates were higher under foraging conditions than in an open field where no prior prey consumption had occurred and no prey odors were present; and 2. tongue-flick rates were elevated after prey consumption. The number of oscillations and the duration of tongue extensions were significantly reduced following tongue-substrate touches, suggesting that tongue contact with the substrate is the immediate stimulus for tongue retraction.

Even in rodents, there is no clear evidence of the existence of sexual pheromones mediating instinctive intersexual attraction. In this review we discuss previous results of our group indicating that female mice reared in the absence of male-derived chemosignals are ‘attracted’ by some components of male-soiled bedding, presumably detected by the vomeronasal organ. In contrast, male odors (olfactory stimuli) only acquire attractiveness by means of their association with the innately ‘attractive’ vomeronasal-detected pheromones. These ‘attractive’ male pheromones are rewarding to adult females, since they induce conditioned preference for a place where they are repeatedly presented to the females. Pheromone reward seems independent of the dopaminergic neurotransmission in the tegmento-striatal pathway, and uses mechanisms and circuits apparently different to those of other natural reinforcers.

The vomeronasal organ (VNO), also known as the Jacobson's organ, is a bilateral chemosensory organ found at the base of the nasal cavity specialized for the detection of higher-molecular weight (non-volatile) chemostimuli. It has been linked to pheromone detection. The VNO has been well studied in nocturnal lemurs and lorises, but poorly studied in diurnal/cathemeral species despite the large repertoire of olfactory behaviors noted in species such as Lemur catta. Here, the VNO and associated structures were studied microanatomically in one adult female and one adult male L. catta. Traditional and immunohistochemical procedures demonstrate the VNO epithelium consists of multiple rows of sensory neurons. Immunoreactivity to Growth-associated protein 43 (GAP43) indicates the VNO is postnatally neurogenic. In volume, the VNO neuroepithelium scales similarly to palatal length compared to nocturnal strepsirrhines. Numerous taste buds present at the oral opening to the nasopalatine duc...

Cet article analyse les controverses scientifiques concernant le rôle des phéromones dans les attirances sexuelles chez l’être humain mais aussi la synchronisation des cycles menstruels chez les femmes. Il détaille les quatre points sur lesquels l’implication des phéromones dans les comportements sexuels humains fait l’objet aussi bien d’affirmations présentées comme des découvertes ou des données acquises, que d’interrogations voire de remises en question : si les phéromones sont des odeurs ou des substances chimiques distinctes, si l’être humain dispose d’un organe fonctionnel idoine à leur détection ou si elles sont captées par le système olfactif principal au même titre que les odeurs, si l’absence de réponse comportementale stéréotypée chez l’être humain permet de maintenir ou non l’hypothèse d’un rôle significatif ou amoindri des phéromones, et enfin, si l’être humain émet ou non des phéromones. L’analyse des publications sur les rôles supposés des phéromones dans l’espèce humaine permet tout autant de mettre en évidence les difficultés méthodologiques dans les expériences menées et les mesures statistiques effectuées, que les variations conceptuelles auxquelles est soumis le vocable de « phéromone ». En regard de la définition des phéromones proposée par Karlson et Lüscher à l’aube des années 1960, la désignation d’hormones stéroïdiennes telles l’androstadiénone ou l’estratetraenol comme des phéromones ne fait pas l’unanimité, alors qu’elle paraît évidente pour un certain nombre de chercheuses et de chercheurs. Apparaît également la diversité des champs scientifiques des chercheurs étudiant les phéromones : biologistes, biochimistes, neuroscientifiques, oto-rhino-laryngologues, zoologues, anthropologues, psychologues… Les enjeux de ces controverses sont multiples : d’une part, elles soulèvent la question des procédés méthodologiques mis en œuvre et des conclusions qu’il est possible de tirer des résultats obtenus ; d’autre part, elles alimentent les débats récurrents sur la part de déterminismes biologiques dans les comportements humains dont les chercheurs en sciences humaines et sociales rendent compte à partir de déterminants sociaux. Cette étude de controverse ne permet pas in fine de considérer comme acquis un quelconque rôle phéromonal dans les comportements sexuels humains.

English version :
This article investigates the ongoing scientific wrangling concerning the role of pheromones in sexual attraction in human beings, and also in the synchronisation of menstrual cycles in females. It looks in detail at the four areas where the involvement of pheromones in sexual behaviour in humans has given rise to affirmations presented as discoveries or acquired data, and at the same time to questions or even challenges: whether pheromones are distinct smells or chemical substances, whether the human being has an appropriate functional organ for detecting them or if they are detected by the main olfactory system in the same way as smells, whether the absence of stereotypical behavioural response in the human being allows the hypothesis of a significant role to be confirmed or disregarded, and finally, whether the human being releases pheromones or not. A review of literature on the hypothetical role of pheromones in humans evidences some methodological difficulties in the experiments conducted and the statistical measurements made, and as many variations in what is understood by the very concept of the word “pheromone”. Looking at the definition of pheromones coined by Karlson and Lüscher at the beginning of the 1960s, steroid hormones such as androstadienone or estratetraenol are considered to be pheromones, and although not everyone agrees with this definition, for other researchers it is undeniable. There are also differences in the scientific specialities of researchers studying pheromones: biologists, biochemists, neuroscientists, ENT specialists, zoologists, anthropologists, psychologists, etc. The stakes of the controversies are high: they raise the question of the methodologies used in the studies and the reliability of their conclusions; they also fuel the regular discussions about the share of biological determinism in human behaviour that researchers in human and social sciences measure based on social determinants. Ultimately, this study of controversy shows that a possible role for pheromones in human sexual behaviour is not something that can by any means be taken for granted.

The vomeronasal organ (VNO) constitutes an accessory olfactory organ that receives chemical stimuli, pheromones, which elicit behavioral, reproductive, or neuroendocrine responses among individuals of the same species. In many macrosmatic animals, the morphological substrate constitutes a separate organ system consisting of a vomeronasal duct (ductus vomeronasalis, VND), equipped with chemosensory cells, and a vomeronasal nerve (nervus vomeronasalis, VNN) conducting information into the accessory olfactory bulb (AOB) in the central nervous system (CNS). Recent data require that the long-accepted dual functionality of a main olfactory system and the VNO be reexamined, since all species without a VNO are nevertheless sexually active, and species possessing a VNO also can sense other than "vomeronasal" stimuli via the vomeronasal epithelium (VNE). The human case constitutes a borderline situation, as its embryonic VNO anlage exerts a developmental track common to most macrosm...

The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don t know either if, or how, visual cues might have direct and developmental effects on hormone levels in other people, the biological basis for the development of visually perceived human physical attraction is currently somewhat questionable. In contrast, the biological basis for the development of physical attraction based on chemical signals is well detailed.

Physiology and pathology have a big deal on tissue morphology, and the intrinsic spatial resolution of an atomic force microscope (AFM) is able to observe ultrastructural details. In order to investigate cellular and subcellular structures in histological sections with the AFM, we used a new simple method for sample preparation, i.e. chemical etching of semithin sections from epoxy resin-embedded specimens:

Squamate reptiles (snakes, lizards, amphisbaenians) rely heavily on chemosensory cues to identify, locate and choose between suitable prey items, but comparatively little research has focused on the chemical ecology of threatened squamate species. Such knowledge highlights ecologically important aspects of their survival. Due to gape limitations, squamates often demonstrate ontogenetic shifts in their diet where they consume larger prey as they grow older and their gape size increases. This shift enables squamates—especially snakes—to exploit new resources in their environments, usually mammalian prey. To test for ontogenetic variation in prey odor responses of a threatened snake species, the Northern pine snake (Pituophis melanoleucus melanoleucus), we presented food-naïve neonates and food-experienced adults with potential prey and non-prey animal scents and quantified their behavioral responses. Our data indicate a strong response to rodent scents from both neonates and adults. Further, neonates showed more frequent investigative probing and retreating behaviors from scented swabs and a higher rate of tongue-flicking than adults. We also developed a new metric for measuring snake responses to prey odor, a tongue-flick reaction score (TFRS), that incorporates investigative behaviors that may be unique to constrictor-type snakes. The TFRS did not differ between age classes and was highest when rodent odors were tested. A canonical discriminant analysis confirmed the relationship between TFRS behavioral components and tested chemical signal reactions. Based on our data, P. melanoleucus may fall into a category of snakes that exhibit an ontogenetic telescope rather than a general ontogenetic shift in their prey odor responses.

The connections of the olfactory bulbs of Podarcis hispanica were studied by tract-tracing of injected horseradish peroxidase. Restricted injections into the main olfactory bulb (MOB) resulted in bilateral terminallike labeling in the medial part of the anterior olfactory nucleus (AON) and in the rostral septum, lateral cortex, nucleus of the lateral olfactory tract, and ventrolateral amygdaloid nucleus. Bilateral retrograde labeling was found in the rostral lateral cortex and in the medial and dorsolateral AON. Ipsilaterally the dorsal cortex, nucleus of the diagonal band, lateral preoptic area, and dorsolateral amygdala showed labeled cell bodies. Retrogradely labeled cells were also found in the midbrain raphe nucleus.Results from injections into the rostral lateral cortex and lateral olfactory tract indicate that the mitral cells are the origin of the centripetal projections of the MOB.Injections in the accessory olfactory bulb (AOB) produced ipsilateral terminallike labeling of the ventral AON, bed nucleus of the accessory olfactory tract, central and ventromedial amygdaloid nuclei, medial part of the bed nucleus of the stria terminalis, and nucleus sphericus. Retrograde labeling of neurons was observed ipsilaterally in the bed nucleus of the accessory olfactory tract and stria terminalis, in the central amygdaloid nucleus, dorsal cortex, and nucleus of the diagonal band. Bilateral labeling of somata was found in the ventral AON, the nucleus sphericus (hilus), and in the mesencephalic raphe nucleus and locus coeruleus.Injections into the dorsal amygdala showed that the mitral neurons are the cells of origin of the AOB centripetal projections. Reciprocal connections are present between AOB and MOB.To our knowledge, this is the first study to address the afferent connections of the olfactory bulbs in a reptile. On the basis of the available data, a discussion is provided of the similarities and differences between the reptilian and mammalian olfactory systems, as well as of the possible functional role of the main olfactory connections in reptiles.

Apically and basally located receptor neurons in the vomeronasal sensory epithelium express Gi2α- and Goα-proteins, V1R and V2R vomeronasal receptors, project to the anterior and posterior accessory olfactory bulb and respond to different stimuli, respectively. The extent to which secondary projections from the two portions of the accessory olfactory bulb are convergent in the vomeronasal amygdala is controversial. This issue is addressed by using anterograde and retrograde tract-tracing methods in rats including electron microscopy. Injections of dextran-amines, Fluoro Gold, cholera toxin-B subunit and Fast Blue were delivered to the anterior and posterior accessory olfactory bulb, bed nucleus of the stria terminalis, dorsal anterior amygdala and bed nucleus of the accessory olfactory tract/anteroventral medial amygdaloid nucleus. We have demonstrated that, apart from common vomeronasal-recipient areas, only the anterior accessory olfactory bulb projects to the bed nucleus of the stria terminalis, medial division, posteromedial part, and only the posterior accessory olfactory bulb projects to the dorsal anterior amygdala and deep cell layers of the bed nucleus of the accessory olfactory tract and the anteroventral medial amygdaloid nucleus. These results provide evidence that, excluding areas of convergence, the V1R and V2R vomeronasal pathways project to specific areas of the amygdala. These two vomeronasal subsystems are therefore anatomically and functionally separated in the telencephalon.