The Accessory Olfactory System Facilitates the Recovery of the Attraction to Familiar Volatile Female Odors in Male Mice.

Odors in female mice induce sexual arousal in male mice. Repeated exposure to female odors attenuates male attraction, which recovers when the odors are removed. The neuronal mechanisms for the recovery of male attraction have not been clarified. In this study, we examined how olfactory systems are involved in the recovery of male attraction to female odors following habituation in mice. Presentation with volatile female odors for 5 min induced habituation in males. To evaluate male attraction to familiar volatile female odors, we measured the duration for investigating volatile female odors from the same female mouse, which was presented twice for 5 min with 1-, 3-, or 5-min interval. Intranasal irrigation with ZnSO4 solution almost completely suppressed investigating behavior, indicating that the main olfactory system is indispensable for inducing the attraction to volatile female odors. In contrast, removal of the vomeronasal organ, bilateral lesions of the accessory olfactory bulb (AOB), or pharmacological blockage of neurotransmission in the AOB did not affect the investigation time at the first odor presentation. However, each one of the treatments decreased the investigation time in the second presentation, compared to that in the first presentation, at longer intervals than control treatment, indicating that the disturbance of neurotransmission in the accessory olfactory system delayed the recovery of the attraction attenuated by the first presentation. These results suggest that the accessory olfactory system facilitates the recovery of the attraction to familiar volatile female odors in male mice.

In vivo stimulus presentation to the mouse vomeronasal system: Surgery, experiment, setup, and software.

BACKGROUND: Achieving controlled stimulus delivery is a major challenge in the physiological analysis of the vomeronasal system (VNS). NEW METHOD: We provide a comprehensive description of a setup allowing controlled stimulus delivery into the vomeronasal organ (VNO) of anesthetized mice. VNO suction is achieved via electrical stimulation of the sympathetic nerve trunk (SNT) using cuff electrodes, followed by flushing of the nasal cavity. Successful application of this methodology depends on several aspects including the surgical preparation, fabrication of cuff electrodes, experimental setup modifications, and the stimulus delivery and flushing. Here, we describe all these aspects in sufficient detail to allow other researchers to readily adopt it. We also present a custom written MATLAB based software with a graphical user interface that controls all aspects of the actual experiment, including trial sequencing, hardware control, and data logging. RESULTS: The method allows measurement of stimulus evoked sensory responses in brain regions that receive vomeronasal inputs. An experienced investigator can complete the entire surgical procedure within thirty minutes. COMPARISON WITH EXISTING METHODS: This is the only approach that allows repeated and controlled stimulus delivery to the intact VNO, employing the natural mode of stimulus uptake. The approach is economical with respect to stimuli, requiring stimulus volumes as low as 1-2µl. CONCLUSIONS: This comprehensive description will allow other investigators to adapt this setup to their own experimental needs and can thus promote our physiological understanding of this fascinating chemosensory system. With minor changes it can also be adapted for other rodent species.

The vomeronasal organ - incidence in a Bulgarian population.

BACKGROUND: The vomeronasal organ is an accessory olfactory organ found in vertebrates that specialises in the chemoreception of pheromones. This study aimed to explore the existence and occurrence of the vomeronasal organ in adult humans. METHODS: A total of 966 consecutive video recordings of out-patient nasopharyngolaryngoscopies performed at the St Marina University Hospital, Varna, Bulgaria, were retrospectively reviewed. RESULTS: Data analysis showed that from the evaluable cases, the organ was evident on the left side of the nasal septum in 14.93 per cent, on the right side in 21.15 per cent and bilaterally in 2.35 per cent of cases. The vomeronasal organ was present in a total of 26.83 per cent of the investigated subjects. CONCLUSION: More research should be focused on revealing the incidence and functionality of the organ, and on its preservation in surgical manipulations that affect the nasal septum and other nearby structures.

Ex vivo preparations of the intact vomeronasal organ and accessory olfactory bulb.

The mouse accessory olfactory system (AOS) is a specialized sensory pathway for detecting nonvolatile social odors, pheromones, and kairomones. The first neural circuit in the AOS pathway, called the accessory olfactory bulb (AOB), plays an important role in establishing sex-typical behaviors such as territorial aggression and mating. This small (<1 mm(3)) circuit possesses the capacity to distinguish unique behavioral states, such as sex, strain, and stress from chemosensory cues in the secretions and excretions of conspecifics. While the compact organization of this system presents unique opportunities for recording from large portions of the circuit simultaneously, investigation of sensory processing in the AOB remains challenging, largely due to its experimentally disadvantageous location in the brain. Here, we demonstrate a multi-stage dissection that removes the intact AOB inside a single hemisphere of the anterior mouse skull, leaving connections to both the peripheral vomeronasal sensory neurons (VSNs) and local neuronal circuitry intact. The procedure exposes the AOB surface to direct visual inspection, facilitating electrophysiological and optical recordings from AOB circuit elements in the absence of anesthetics. Upon inserting a thin cannula into the vomeronasal organ (VNO), which houses the VSNs, one can directly expose the periphery to social odors and pheromones while recording downstream activity in the AOB. This procedure enables controlled inquiries into AOS information processing, which can shed light on mechanisms linking pheromone exposure to changes in behavior.

Vomeronasal organ lesion disrupts social odor recognition, behaviors and fitness in golden hamsters.

Most studies support the viewpoint that the vomeronasal organ has a profound effect on conspecific odor recognition, scent marking and mating behavior in the golden hamster (Mesocricetus auratus). However, the role of the vomeronasal organ in social odor recognition, social interaction and fitness is not well understood. Therefore, we conducted a series of behavioral and physiological tests to examine the referred points in golden hamster. We found that male hamsters with vomeronasal organ lesion showed no preference between a predator odor (the anal gland secretion of the Siberian weasels (Mustela sibirica) and putative female pheromone components (myristic acid and palmitic acid), but were still able to discriminate between these 2 kinds of odors. In behavioral tests of anxiety, we found that vomeronasal organ removal causes female hamsters to spend much less time in center grids and to cross fewer center grids and males to make fewer crossings between light and dark boxes than sham-operated controls. This indicates that a chronic vomeronasal organ lesion induced anxious responses in females. In aggressive behavioral tests, we found that a chronic vomeronasal organ lesion decreased agonistic behavior in female hamsters but not in males. The pup growth and litter size show no differences between the 2 groups. All together, our data suggested that vomeronasal organ ablation disrupted the olfactory recognition of social chemosignals in males, and induced anxiety-like and aggressive behavior changes in females. However, a vomeronasal organ lesion did not affect the reproductive capacity and fitness of hamsters. Our studies may have important implications concerning the role of the vomeronasal organ in golden hamsters and also in rodents.

Órgano vomeronasal: estudio anatómico de prevalencia y su función / The vomeronasal organ: anatomic study of prevalence and its role

Introducción: El órgano vomeronasal (OVN) descrito por Jacobson en mamíferos distintos al ser humano, es una incógnita tanto en lo que se refiere a su localización así como a su función en la raza humana. Se considera como un vestigio del olfato, que en los animales mamíferos parece influir en los hábitos sexuales (feromonas) y sociales. Hasta la fecha han sido escasos los estudios concluyentes al respecto en humanos. Objetivo: Conocer la prevalencia del órgano vomeronasal en nuestras consultas. Material y método: Presentamos un estudio prospectivo de prevalencia de la frecuencia de aparición de dicho órgano en 150 sujetos distribuidos por edad y sexo, explorados por endoscopia nasosinusal rígida. Por otro lado, analizamos la influencia sobre la libido (normal-disminuida-aumentada) en el posoperatorio de 35 septoplastías, a los 15 días tras retirada de taponamiento nasal y a los 30 días y lo comparamos con un grupo de 40 pacientes intervenidos timpanoplastías. Resultados: Estudiados 150 sujetos, encontramos la presencia del órgano vomeronasal en el 39,33% (59), de los cuales el 72,88% (43) fue unilateral (23 derecha y 20 izquierda) y el 27,12% (16) bilateral. En 91 (60,67%) no hallamos dicha estructura. La libido de los 35 pacientes intervenidos de septoplastía estaba disminuida, a los 15 días, en el 77,14% (27) frente al 40% (16) de las timpanoplastías, normal en el 17,14% (6) frente al 50% (20) de las cirugías otológicas, y en 2 (5,7%) poseptoplastía había aumentado, frente al 10% (4) del otro grupo. A los 30 días, en el 77,14% (27) de las septoplastías se había normalizado frente al 90% (36) del grupo otológico, en 2 (5,71%) de la cirugía nasal continuaba disminuida frente al 10% (4) del grupo de las timpanoplastías y en 6 (17,14%) tras septoplastía había aumentado. A todos los pacientes se les aplicó el mismo test no normalizado. Conclusión: El órgano vomeronasal de Jacobson continúa siendo un gran desconocido. Es una estructura que, al parecer, no es constante, al menos a la exploración endoscópica nasosinusal. Es difícil valorar si la cirugía en sí misma o el trauma psicológico posquirúrgico son los que afectan la libido de los pacientes tras la cirugía.

Introduction: The vomeronasal organ (OVN) described by Jacobson in mammals other than humans is unknown both in terms of its location and its role in the human race. It is viewed as a vestige of smell, that mammals in the animal seems to influence the sexual habits (pheromone) and social. To date, few studies have been inconclusive on this in humans. Aim: To determine the prevalence of vomeronasal organ in our medical consultations. Materials and methods: We report a prospective prevalence study of the occurrence of such a body in 150 subjects distributed by age and sex explored by endoscopic sinus rigid. On the other hand, we analyze the effect on the libido (normally less-plus) in the postoperative 35 septoplasty, 15 days after the withdrawal of nasal pack and 30 days and compared with a group of 40 tympanoplasty surgery. Results: Studied 150 subjects, we found the presence of the vomeronasal organ in 39.33% (59), of which 72.88% (43) had unilateral (23 right and 20 left) and 27.12% (16) bilaterally. In 91 (60.67%) did not find such a structure. The libido of the 35 patients who underwent septoplasty was decreased at 15 days, at 77.14% (27) versus 40% (16) of tympanoplasty, normal in 17.14% (6) compared to 50% (20) of otologic surgery, and in 2 (5.7%) postseptoplasty had increased, compared to 10% (4) the other group. At 30 days, in 77.14% (27) of the septoplasty group the libido was normalized against 90% (36) in the otologic group. In 2 cases (5.71%) of nasal surgery group was still decreased versus 10% (4) of cases of the tympanoplasty group, and in 6 (17.14%) postseptoplasty was increased. All patients were administered the same test is not standardized. Conclusion: The vomeronasal organ of Jacobson remains the great unknown. It is a structure that apparently is not constant, at least in the endoscopic sinus exploration. With regard to their role, it is difficult to assess whether the psychological trauma after surgery or the surgery by itself is responsible of the libido changes.

Alarm pheromone is detected by the vomeronasal organ in male rats.

It is widely known that a stressed animal releases specific pheromones, possibly for alarming nearby conspecifics. We previously investigated an alarm pheromone in male rats and found that this alarm pheromone evokes several responses, including increases in the defensive and risk assessment behaviors in a modified open-field test, and enhancement of the acoustic startle reflex. However, the role of the vomeronasal organ in these pheromone effects remains unclear. To clarify this point, vomeronasal organ-excising or sham surgeries were performed in male rats for use in 2 experimental models, after which they were exposed to alarm pheromone. We found that the vomeronasal organ-excising surgery blocked the effects of this alarm pheromone in both the modified open-field test and acoustic startle reflex test. In addition, the results of habituation/dishabituation test and soybean agglutinin binding to the accessory olfactory bulb suggested that the vomeronasal organ-excising surgery completely ablated the vomeronasal organ while preserving the functioning of the main olfactory system. From the above results, we showed that the vomeronasal organ plays an important role in alarm pheromone effects in the modified open-field test and acoustic startle reflex test.

Adult testosterone treatment but not surgical disruption of vomeronasal function augments male-typical sexual behavior in female mice.

It was recently reported that female mice lacking a functional vomeronasal organ (VNO) displayed male-typical sexual behavior indiscriminately toward female and male conspecifics. These results have been cited as showing that a circuit controlling male-typical sex behavior exists in both sexes, with its activation in females being tonically inhibited by VNO signaling, independent of adult sex hormones. We further assessed this hypothesis while controlling the endocrine status of female mice in which VNO function was surgically disrupted. In experiment 1, VNO-lesioned (VNOx) female mice showed no more mounting or pelvic-thrusting behavior toward an estrous female or a castrated, urine-swabbed male (presented simultaneously) than sham-operated (VNOi) females. This was true when subjects were either ovary-intact or ovariectomized and treated with estradiol, estradiol plus progesterone, or testosterone. In experiment 2, female mice given accessory olfactory bulb lesions or a sham lesion displayed equivalent frequencies of male sex behaviors when given testosterone after ovariectomy. In experiment 3, VNOx and VNOi females displayed equivalent frequencies of male sex behaviors toward an estrous female or a castrated male (presented in separate tests), again, when given testosterone after ovariectomy. Our results confirm early reports that adult testosterone can stimulate appreciable male-typical sex behavior in female mice. However, we failed to corroborate the recent claim that VNO signaling normally inhibits the activity of neural circuitry controlling the expression of male-typical mating behavior by female mice.

A functional circuit underlying male sexual behaviour in the female mouse brain.

In mice, pheromone detection is mediated by the vomeronasal organ and the main olfactory epithelium. Male mice that are deficient for Trpc2, an ion channel specifically expressed in VNO neurons and essential for VNO sensory transduction, are impaired in sex discrimination and male-male aggression. We report here that Trpc2-/- female mice show a reduction in female-specific behaviour, including maternal aggression and lactating behaviour. Strikingly, mutant females display unique characteristics of male sexual and courtship behaviours such as mounting, pelvic thrust, solicitation, anogenital olfactory investigation, and emission of complex ultrasonic vocalizations towards male and female conspecific mice. The same behavioural phenotype is observed after VNO surgical removal in adult animals, and is not accompanied by disruption of the oestrous cycle and sex hormone levels. These findings suggest that VNO-mediated pheromone inputs act in wild-type females to repress male behaviour and activate female behaviours. Moreover, they imply that functional neuronal circuits underlying male-specific behaviours exist in the normal female mouse brain.

A rare case of jugular foramen schwannoma arising from Jacobson's nerve.

The jugular foramen (JF) region is a complex area of the cranial base where venous structures such as the jugular bulb and the inferior petrosal sinuses are strictly related to the lower cranial nerves IX, X and XI. The most common tumours include glomus jugulare, schwannomas of the mixed cranial nerves (IX-XI) and meningiomas. Schwannomas involving the jugular foramen are rare neoplasms and in most of the cases are thought to originate from the X cranial nerve. We report a case of a schwannoma of the JF diagnosed at an early stage, allowing radiological and surgical evidence to support its origin from the tympanic branch of the IX cranial nerve. To our knowledge this is the first case reported in the literature of such a tumour.

Removal of the vomeronasal organ blocks the stress-induced hyperthermia response to alarm pheromone in male rats.

Previously, we reported that male Wistar rats release alarm pheromone from their perianal region, which aggravates stress-induced hyperthermia (SIH) in pheromone-recipient rats. The subsequent discovery that this pheromone could be trapped in water enabled us to expose recipients to the pheromone in their home cages. Despite its apparent influence on autonomic and behavioral functions, we still had no clear evidence as to whether the alarm pheromone was perceived by the main olfactory system (MOS) or by the vomeronasal system. In this study, we investigated this question by exposing 3 types of recipients to alarm pheromone in their home cages: intact males (Intact), vomeronasal organ-excised males (VNX), and sham-operated males (Sham). The Intact and Sham recipients showed aggravated SIH in response to alarm pheromone, whereas the VNX recipients did not. In addition, the results of the habituation/dishabituation test and soybean agglutinin binding to the accessory olfactory bulb verified the complete ablation of the vomeronasal organ (VNO) with a functional MOS in the pheromone recipients. These results strongly suggest that male rats perceive alarm pheromone with the VNO.

The severely deviated septum--the way I solve the problem.

Surgical correction of severely deviated or "saddle" noses poses specific problems that are often difficult to resolve because of the complexity of the deformities, particularly those of the septum. Four steps are necessary: (1) the deformations must be skeletonized and visualized by a perfect extramucosal dissection and maxillary-premaxillary approaches; (2) the septum must be mobilized by resection of the osteocartilaginous chondrovomerine callus, after which it is possible to carry out the septum as long as the mucosa is not torn; (3) the angulations must be corrected carrying out discontinuous cartilaginous incisions; and (4) the structures must be stiffened. Polydioxanone (PDS) struts provide a neat solution to the issue of the reconstruction of a plane and sufficiently stiff septum.

Gonadotropin-releasing hormone (GnRH) immunoreactive neurons in male mouse lemurs following removal of the vomeronasal organ.

Removal of the vomeronasal organ (VNO) in male mouse lemurs led to an increase in the number of immunoreactive gonadotropin-releasing hormone (GnRH) neurons in the medial preoptic area, compared to control males. No difference was found in the mediobasal hypothalamus. In this primate, which presents a fully functional VNO, the anterior part of the hypothalamus could be the major target for VNO-mediated regulation of GnRH function and the subsequent modulation of chemosensory dependent reproductive behavior.

Enlarged vomeronasal organ in a child: imaging findings.

The vomeronasal organ is a special sensory organ that exists in both animals and humans. It is located on the sides of nasal septum and although it involutes with age, occasionally it may be seen in humans. We present the imaging findings in a child with an enlarged nasal septum whose features we believe are compatible with a vomeronasal organ.

Mice (Mus musculus) lacking a vomeronasal organ can discriminate MHC-determined odortypes.

Major histocompatibility complex (MHC) genes in mammals (H-2 in mice) play a major role in regulating immune function. They also bestow individuality in the form of a chemical signature or odortype. At present, the respective contributions of the olfactory epithelium and the vomeronasal organ (VNO) in the recognition of individual odortypes are not well defined. We examined a possible role for the VNO in the recognition of MHC odortypes in mice by first removing the organ (VNX) and then training the mice to distinguish the odors of two congenic strains of mice that differed only in their MHC type. C57BL/6J mice (bb at H-2) and C57BL/6J-H-2(k) (kk at H-2) provided urine for sensory testing. Eight VNX and six sham-operated mice were trained to make the discrimination. Neither the number of training trials-to-criterion nor the rate of learning differed significantly for VNX and sham-operated mice. We conclude that the VNO is not necessary for learning to discriminate between MHC odortypes.

Pre-exposure to female chemosignals or intracerebral GnRH restores mating behavior in naive male hamsters with vomeronasal organ lesions.

Chemosensory input is essential for mating in male hamsters and the vomeronasal organ is critical to mating in naive males. In studies to investigate the convergence of vomeronasal chemosensory input and the neurohormone gonadotrophin releasing hormone (GnRH), we have unexpectedly found that pre-exposure to pheromone-containing chemosignals from female hamsters will also eliminate mating deficits normally seen in naive male hamsters with vomeronasal organs removed (VNX). In the present studies, naive-intact and naive-VNX male hamsters were given intracerebroventricular injections of GnRH or saline and exposed to female pheromones found in hamster vaginal fluid (HVF) or to water 40 min prior to a 5 min mating test. VNX males given saline injections and exposed to water had severe mating deficits, but VNX males given saline injections and exposed to HVF mated normally. As shown previously, males given GnRH injections and exposed to water also mated normally. HVF exposure prior to a mating test apparently acted to compensate for the lack of vomeronasal input in these males.

Lesions of the vomeronasal organ disrupt mating-induced pair bonding in female prairie voles (Microtus ochrogaster).

The prairie vole (Microtus ochrogaster) is a highly social, monogamous species and displays pair bonding that can be assessed by the presence of selective affiliation with the familiar partner versus a conspecific stranger. In female prairie voles, exposure to a male or to male sensory cues is essential for estrus induction, and the subsequent mating facilitates pair bond formation. In the present study, we examined the role of the vomeronasal organ (VNO) in estrus induction and pair bonding in female prairie voles. VNO lesions did not alter olfaction mediated by the main olfactory system, but did prevent male-induced estrus induction. We by-passed the necessity of the VNO for estrus induction by estrogen priming the females. Despite the fact that all subjects displayed similar levels of mating, social contact and locomotor activities, VNO lesioned females failed to show mating-induced pair bonding whereas intact and sham-lesioned females displayed a robust preference for the familiar partner. Our data not only support previous findings that the VNO is important for estrus induction but also indicate that this structure is crucial for mating-induced pair bonding, suggesting an important role for the VNO in reproductive success in prairie voles.

The vomeronasal organ is involved in discrimination of individual odors by males but not by females in golden hamsters.

The vomeronasal organ (VNO) has a wide variety of functions in terrestrial vertebrates, some of which involve responses to classical pheromones whereas others do not. We examined the role of the VNO in discrimination of individual differences in odors of male and female golden hamsters using a habituation paradigm. Removal of the VNO resulted in elimination of the ability of male hamsters to discriminate between some individually distinctive odors (e.g., flank gland secretion), but not others (e.g., urine). In females, such lesions had no effect. The type of test trial also influenced the results; in test trials employing a single, novel odor, removal of the VNO in males did have an effect but in test trials in which both the novel and the familiar odor were presented, VNO removal had no effect. It is concluded that (a) there is a sex difference in the role of the VNO in the discrimination of individual odors, (b) the role of the VNO in discrimination of individual odors varies from odor to odor, and (c) deficits due to VNO removal are more readily observed in more difficult tasks.