Patent nasopalatine ducts: Evidence to support persistence of the vomeronasal system?

The vomeronasal system is comprised of the nasopalatine duct and the vomeronasal organ. While this system functions in chemodetection in mammals, its presence and function in adult humans remains to be clearly elucidated. Here, a case of asymptomatic, bilateral, patent nasopalatine ducts is presented. We postulate that the presence of these patent structures represents persistence of the embryological nasopalatine duct component of the vomeronasal organ into adult life

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Detection of conspecific pheromones elicits fos expression in GABA and calcium-binding cells of the rat vomeronasal system–medial extended amygdala

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The olfactory accessory system is specialized in the detection of pheromones, being an afferent to medial extended amygdala. In spite of the fact that numerous phenotypes are found in these structures, in the current literature, there are no detailed descriptions about the phenotype of neurons in the vomeronasal system–medial extended amygdale after their activation by pheromonal stimuli. Using immunohistochemistry for fos and dual immunohistochemistry for fos and phenotypes, here we show that females have a greater number of activated neurons by the pheromonal stimulus. Likewise, a great colocalization of fos with GABA, calretinin, and calbindin was observed in the vomeronasal system–medial extended amygdala. These data suggest that in amygdaloid areas, neuronal excitability is controlled by GABAergic neurons that contain different calcium-binding proteins, indicating the important role of inhibitory control on the incoming sensory pheromonal and olfactory inputs controlled and processed by the vomeronasal system (AU)

Receptores de feromonas de mamíferos: supervivencia y sexualidad / Mammalian pheromone receptors: survival and sexuality

En 1995 Catherine Dulac y Richard Axel publicaron la existencia de una nueva familia de genes que codificaban los posibles receptores de feromonas, pertenecientes a la amplia familia de los de siete hélices transmembranares y acoplados a proteínas G. Desde entonces se han clonado nuevos genes que han sido agrupados en dos familias, los receptores vomeronasales tipo 1 y 2, V1R y V2R, con diferente estructura y situados con diferente distribución en el órgano vomeronasal. La naturaleza química de las feromonas y de las proteínas que las asocian y transportan conocidas como lipocalinas es otro de los aspectos de los que se dispone de abundante información. Los mecanismos de transducción de la señal mediada por feromonas sobre los receptores V1R y V2R implican la activación de la fosfolipasa C tipo β2, PLCβ2, generando el fosfatidilinositol trifosfato y el diacilglicerol en la cara interna de la membrana neuronal. El diacilglicerol es un ligando endógeno, que permite la apertura del canal de la familia TRPC (Transient Receptor Potential Channel) denominado TRPC2 que se abre y deja pasar iones Ca2+ y Na+ al interior de la neurona sensorial, iniciando la despolarización de la membrana y originando el potencial de acción. La señal eléctrica es conducida al bulbo olfativo auxiliar por axones que llegan de modo disperso y establecen conexión con las células mitrales, las cuales envían sus prolongaciones hasta el sistema límbico y otras estructuras cerebrales, donde influencian o provocan las respuestas de supervivencia de la especie, entre ellas las de apareamiento y agresividad. Un aspecto relevante desde el punto de vista evolutivo es que en primates el gen TRPC2 es un pseudogen sin funcionalidad y por lo tanto el órgano vomeronasal es un vestigio carente de función. Recientes estudios indican que la captación de feromonas en primates se realiza a través del epitelio olfativo y el bulbo olfativo principal e incluso en otros mamíferos esta estructura parece mediar en algunas respuestas especie específicas

In 1995 Catherine Dulac and Richard Axel discovered a new gene family corresponding to the pheromone receptors. They were members of the seven transmembrane helix coupled to G proteins. Since then, new genes have been clonned and grouped according their sequence homology in two main families of vomeronasal receptors the V1R and the V2R. They exhibit different distribution pattern at the vomeronasal epithelium, where they are coupled to different G proteins. The chemical nature of the mammalian pheromones is very diverse and can associate with proteins called lipocalins to reach the vomeronasal organ. The transduction mechanisms of pheromone receptors, V1R and V2R, require respectively a Gi and a Go proteins, to further activate a phospholipase C, the PLCβ2. This enzyme hydrolyses the phosphatidyl inositol located at the plasma membrane originating phosphatidylinositol triphosphate and diacylglycerol. Diacylglycerol is an endogenous ligand that opens the TRPC2 channel (Transient Receptor Potential Channel), allowing the entrance of cations, mostly Ca2+ y Na+. The membrane depolarisation at the vomeronasal neuron originates the action potential that is sent to the accessory olfactory bulb by the axon, which in a different way as those from the main olfactory epithelia, do not organise the axonal prolongations and reach the mitral neurones in a disperse way, without forming a glomerular structure, afterwards the mitral cells send their axons to the limbic system and other cerebral structures related to aggressive behaviour and mating. It is relevant to underline that in monkeys from the old world and primates including humans, the vomeronasal organ is only a vestigial structure without function. The reason relies on the TRPC2 gene, which is a pseudo gene, without physiological function. Recent experimental approaches have demonstrated that the sensing of some pheromonal signals in these species, and also in mammals with a functional vomeronasal organ, can be carried out by the main olfactory epithelia through the main olfactory bulb. This structure being also connected to the hypothalamus, where neurones releasing LHRH can control sexual behaviour. These data confirm the broad possibilities of signalling through pheromones and that much effort is still required to fully understand their possibilities

Controversies on the human vomeronasal system / Controversias acerca del sistema vomeronasal humano

Most vertebrates possess an accessory olfactory system parallel to the olfactory system. The most peripheral structure of the accessory (or vomeronasal) system is the vomeronasal organ, located at the base of the nasal septum. From the vomeronasal organ, vomeronasal sensory neurons project to the accessory olfactory bulb, which in turn projects to the vomeronasal-recipient structures in the basal telencephalon. The vomeronasal system detects pheromones (substances generally emitted by conspecifics) or prey chemicals, which have been demonstrated to be critical for sexual behaviors and foraging, respectively. In humans, the existence and functionality of the vomeronasal system has been debated for the last three centuries. Recent anatomical, histological, behavioral and physiological studies have reached very different conclusions on this issue, leaving an old controversy unresolved. A review of the literature indicates that most of evidence for a functional human vomeronasal system has been provided by physiological studies conducted by a single research group. Since current anatomical evidence does not support the existence of neural substrates for these physiological effects, the functionality of the human vomeronasal organ awaits further independent confirmation (AU)

La mayoría de los vertebrados poseen un sistema olfativo accesorio paralelo al sistema olfativo. La estructura más periférica del sistema accesorio (o vomeronasal) es el órgano vomeronasal, localizado en la base del septo nasal. Del órgano vomeronasal proyectan neuronas sensoriales vomeronasales hacia el bulbo olfatorio accesorio, que a su vez proyecta hacia las estructuras receptoras vomeronasales en el telencéfalo basal. El sistema vomeronasal detecta a la feromonas (sustancias que suelen ser emitidas por conespecíficos) o agentes químicos de presa, los cuales se ha mostrado que son cruciales para el comportamiento sexual y la búsqueda, respectivamente. En los seres humanos, la existencia y funcionalidad del sistema vomeronasal ha sido debatido a lo largo de los últimos tres siglos. Estudios anatómicos, histológicos, conductuales y fisiológicos recientes han descrito conclusiones bien diferentes en cuanto a este aspecto se refiere, dejando una controversia antigua sin explicación. Una revisión de la literatura revela que la mayoría de las evidencias en apoyo de la existencia de un sistema vomeronasal en los seres humanos procede de estudios fisiológicos llevados a cabo por un único equipo de investigación. Puesto que los hallazgos anatómicos actuales no apoyan la existencia de sustratos nerviosos para estos efectos fisiológicos, la funcionalidad del órgano vomeronasal humano queda pendiente de confirmación independiente adicional (AU)