Histomorphology of vomeronasal organ in Scincella tsinlingensis / Histomorfología del órgano vomeronasal en Scincella tsinlingensis

Due to the great change in the morphology of squamate vomeronasal organ (VNO), the histomorphology characteristics of VNO in Scincella tsinlingensis were studied by light and electronic microscopy. The results indicated that the VNO of S. tsinlingensis was located at the base of nasal cavity and consisted of a mushroom body situated anteroventrally and a sensory epithelium (SE) situated dorsocaudally. SE was composed of supporting cells, receptor cells and basal cells, and the supporting cells contained secretory granules near the surface membrane. Most of receptor cells were irregular in shape with long cytoplasmic extensions and characterized by microtubules, vesicles, and mitochondria. The basal cells with long cytoplasmic extensions were also irregular in shape and appeared a greater electron density than others. The thick nerve bundles were found on the dorsomedial area of VNO, and the surface of mushroom body was non-sensory epithelium consisting of ciliated and basal cells, without goblet cells. Epithelial cells were arranged in irregular, with many cilia and microvilli distributed on its free surface. Cells on the basal layer were irregularly circular in shape and arranged sparsely. Taken together, the results indicated that the fine structure of VNO in S. tsinlingensis was similar to other species from scincomorphs.

Debido al gran cambio en la morfología del órgano vomeronasal (OVN), se estudiaron las características histomorfológicas en la Scincella tsinlingensis por microscopías de luz y electrónica. Los resultados indicaron que el OVN de S. tsinlingensis se localizaba en la base de la cavidad nasal y consistía en un cuerpo como hongo situado anteroventralmente y un epitelio sensorial (ES) situado dorso caudamente. El ES estaba compuesto de células de soporte, células receptoras y células basales, y las células de soporte contenían gránulos secretores cerca de la membrana superficial. En gran parte de la mayoría de las células receptoras se observó una forma irregular con largas extensiones citoplasmáticas, caracterizadas por microtúbulos, vesículas y mitocondrias. Las células basales con extensiones citoplasmáticas también tenían forma irregular y algunas parecían tener una mayor densidad de electrones. Los haces gruesos nerviosos se encontraron en el área dorsomedial del OVN, la superficie del cuerpo de estaba compuesto de epitelio no sensorial y consistía de células ciliadas y basales, sin células caliciformes. Las células epiteliales estaban dispuestas de manera irregular, con muchos cilios y microvellosidades distribuidas en su superficie libre. Las células en la capa basal eran escasas y de forma circular irregular. Tomados en conjunto, los resultados indicaron que la estructura fina del OVN en S. tsinlingensis era similar a otras especies de scincomorpha.

Nervus terminalis and nerves to the vomeronasal organ: a study using human fetal specimens / 대한해부학회지

The human nervus terminalis (terminal nerve) and the nerves to the vomeronasal organ (VNON) are both associated with the olfactory nerves and are of major interest to embryologists. However, there is still limited knowledge on their topographical anatomy in the nasal septum and on the number and distribution of ganglion cells along and near the cribriform plate of the ethmoid bone. We observed serial or semiserial sections of 30 fetuses at 7–18 weeks (crown rump length [CRL], 25–160 mm). Calretinin and S100 protein staining demonstrated not only the terminal nerve along the anterior edge of the perpendicular lamina of the ethmoid, but also the VNON along the posterior edge of the lamina. The terminal nerve was composed of 1–2 nerve bundles that passed through the anterior end of the cribriform plate, whereas the VNON consisted of 2–3 bundles behind the olfactory nerves. The terminal nerve ran along and crossed the posterior side of the nasal branch of the anterior ethmoidal nerve. Multiple clusters of small ganglion cells were found on the lateral surfaces of the ethmoid's crista galli, which are likely the origin of both the terminal nerve and VNON. The ganglions along the crista galli were ball-like and 15–20 µm in diameter and, ranged from 40–153 in unilateral number according to our counting at 21-µm-interval except for one specimen (480 neurons; CRL, 137 mm). An effect of nerve degeneration with increasing age seemed to be masked by a remarkable individual difference.

Morphology of cat vomeronasal organ non-sensory epithelium during postnatal development / 대한해부학회지

The vomeronasal organ has an important role in mammal's social and sexual behaviours. In addition, it mediates defensive behavior through detection of protein pheromone homologues. In this work, a detailed morphological description of the postnatal development of the non-sensory epithelium (NSE) lining the vomeronasal duct (VND) of the female cat is provided using various histological techniques. The study focused on newborn, 2 weeks, 4 weeks, and 8 weeks of postnatal ages using four animals for each age. We report here for the first time that three types of NSE line the rostral segment of the VND; nonkeratinized stratified squamous epithelium, stratified cuboidal epithelium, and ciliated pseudo stratified columnar ciliated epithelium with goblet cells and that the VND undergoes 90° a change in its its axis from the vertical position caudally to the horizontal position rostral. The NSE which lines the lateral side of the VND middle segment is consists of cliated pseudostratified columnar epithelium without goblet cells. In addition to basal cells, the NSE contains ciliated and three types of nonciliated columnar epithelial cells (dark, light, and unstained). Mitotic figures were observed only in the basal cells layer during the first 2 weeks of postnatal development. Intraepithelial invading inflammatory cells were uncommon. Scanning electron microscopy revealed unevenly distributed long cilia intermingled with microvillar processes and intervening short microvillar processes. These projecting cilia and microvilli revealed a gradual increase in their height during development toward maturity.

Expression of neuronal and non-neuronal markers in the vomeronasal organs of one-humped camel (Camelus dromedarius) and Egyptian water buffalo (Bubalus bubalis) / Expresión de marcadores neuronales y no neuronales en los órganos vomeronasales del camello jorobado y el búfalo egipcio de agua

Fourteen vomeronasal organs (VNOs) of adult males one-humped camels (Camelus dromedarius) and Egyptian water buffaloes (Bubalus bubalis) (n=7/each) were examined immunohistochemically with neuronal markers; synaptophysin (SYP) and glial fibrillary acidic protein (GFAP) to clarify the distribution of the vomeronasal (VN) receptor cells and nerve fibers, in addition to elucidate the existence of non-neuronal elements via S-100 and endothelial nitric oxide synthase (eNOS). In both animals, the VNO was lined medially with VN sensory (olfactory) epithelium and non-sensory (respiratory) epithelium laterally. Immunohistochemically, both animals showed SYP immunolabeling only in the receptor cells of VN sensory epithelium while GFAP labeled the ensheathing cells of the nerve fibers of VNOs. Both S-100 and eNOS labeled non-neuronal elements of the VNO; the supporting cells of sensory epithelium and the VN glands. In view of these observations, we postulate that the VNOs of both animals contain various cells populations that express several neuronal and non-neuronal markers. As well as, SYP and GFAP are suggested as markers for receptor cells and ensheathing cells of nerves of the VNOs respectively. However, no clear differences can be detected in the expressions of neuronal and non-neuronal markers in VNOs of camel and buffalo since they are ruminant species.

En este estudio fueron examinados 14 órganos vomeronasales (OVN) de machos adultos de camellos de una joroba (Camelus dromedarius) y búfalos egipcios de agua (Bubalus bubalis) (n = 7 / cada uno) por inmunohistoquímica con marcadores neuronales, sinaptofisina (SIP) y proteína ácida fibrilar glial (PAFG), para identificar la distribución vomeronasal (VN) del receptor de células y fibras nerviosas, además de dilucidar la existencia de elementos no neuronales a través de S-100 y óxido nítrico sintasa endotelial (ONSe). En ambos animales, el OVN se encuentra alineado en sentido medial con el epitelio sensorial (olfato) y lateralmente con el epitelio no sensorial (respiratorio). En el estudio inmunohistoquímico, ambos animales mostraron marcadores inmunológicos solamente en las células receptoras del epitelio sensorial VN, mientras que la proteína ácida fibrilar glial marcaba las fibras nerviosas de OVN. Tanto el S-100 como la óxido nítrico sintasa endotelial, marcaron elementos no neuronales del OVN, las células de revestimiento del epitelio sensorial y las glándulas VN. En relación a estas observaciones, se postula que los OVN de ambos animales contienen células que expresan varios marcadores neuronales y no neuronales. SIP y la PAFG se sugieren como marcadores para células receptoras y las células gliales de nervios del OVN, respectivamente. Sin embargo, debido a que son especies de rumiantes, no existen diferencias claras que se puedan detectar en las expresiones de los marcadores neuronales y no neuronales en el OVN de camello y búfalo.

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.

Morphological characterization of the nasopalatine region in human fetuses and its association to pathologies

The nasopalatine region is composed of structures such as the vomeronasal organ and nasopalatine duct. The nasopalatine duct may provide the communication of the mouth to the nasal cavity in human fetuses and can be obliterated in an adult human. Knowledge on the development of the nasopalatine region and nasopalatine duct in humans is necessary for understanding the morphology and etiopathogenesis of lesions that occur in this region. Objective The aim of the present study was to describe the morphological aspects of the nasopalatine region in human fetuses and correlate these aspects with the development of pathologies in this region. Material and Methods Five human fetuses with no facial or palatine abnormalities were used for the acquisition of specimens from the nasopalatine region. After demineralization, the specimens were histologically processed. Histological cuts were stained with methylene blue to orient the cutting plane and hematoxylin-eosin for the descriptive histological analysis. Results The age of the fetuses was 8.00, 8.25, 9.00 and 9.25 weeks, and it was not possible to determine the age in the last one. The incisive canal was observed in all specimens as an opening delimited laterally by the periosteum and connecting oral and nasal cavity. The nasopalatine duct is an epithelial structure with the greatest morphological variation, with either unilateral or bilateral occurrence and total patent, partial patent and islet forms. The vomeronasal organ is a bilateral epithelized structure located alongside the nasal septum above the incisive canal in all the fetuses. Conclusions The incisive canal, nasopalatine duct and vomeronasal organ are distinct anatomic structures. The development of nasopalatine duct cysts may occur in all forms of the nasopalatine duct. .

A morphological study of vomeronasal organ of Korean black goat (Capra aegagrus hircus) / 대한수의학회지

The vomeronasal organ (VNO) plays an important role in reproduction and social activities in ruminants including goats. A morphological study on the structure of VNO and its epithelial cells was carried out in Korean black goats. Grossly, the VNO of Korean goats opens into mouth through incisive ducts. Microscopically, the epithelium of VNO consisted of medial sensory epithelium and lateral non-sensory epithelium. Several blood vessels and nerve bundles were observed in the lamina propria encased by vomeronasal cartilage. Immunohistochemical staining showed that protein gene product (PGP) 9.5 was immunostained in the receptor cells of the sensory epithelium and in some cells of the non-sensory epithelium. Galectin-3 was mainly observed in the supporting cells of sensory and non-sensory epithelium. Lectins including wheat germ agglutinin, Ulex europaeus agglutinin, Bandeiraea simplicifolia lectin Isolectin B4, Dolichos biflorus agglutinin and soybean agglutinin used in this study were bound in VNO sensory, non-sensory epithelia as well as in the lamina propria with varying intensity. Collectively, this is a first descriptive morphological study of VNO of Korean black goat with special reference to lectin histochemistry.

Histochemical study of lectin-binding patterns in the rat vomeronasal organ during postnatal development / 대한수의학회지

Histochemical patterns of lectin binding during development of the rat vomeronasal organ (VNO) were studied to determine whether glycoconjugates are differently expressed after birth. Three types of lectins, Dolichos biflorus agglutinin (DBA), wheat germ agglutinin (WGA), and Ulex europaeus agglutinin I (UEA-I), were studied histochemically in the rat VNO at various stages post-birth: postnatal days 1 and 7, the preweaning period (4 weeks after birth), and at sexual maturity (8 weeks after birth). The free border of the vomeronasal sensory epithelium was positive for both WGA and UEA-I in rats of all ages; whereas, VNO receptor cells and supporting cells were positive only for both WGA and UEA-I from 4 weeks after birth. DBA reactivity was detected in the free border but less so in receptor cells and supporting cells. WGA and UEA-I, but not DBA, showed similar patterns in various ages. In the Jacobson's gland, WGA, UEA-I and DBA were detected in some acini from 4 weeks after birth but not at postnatal days 1 or 7. Collectively, reactivity for three lectins, WGA, UEA-I and DBA, increased in receptor cells and gland acini during postnatal development, possibly contributing to the enhanced chemoreception in rats.

The Odorant Signaling Pathway

Through the sense of smell mammals can obtain information about food, danger, sexual partners and predators. Two main different types of signals can be recognized by the olfactory system: volatile odorants, which are detected by the olfactory sensory neurons of the nose; and pheromones, which are detected by the vomeronasal neurons of the accessory olfactory system, or vomeronasal organ. These sensory neurons express respectively hundreds of odorant and pheromone receptors, which belong to the superfamily of G protein-coupled receptors. We review the general organization of the main and accessory olfactory systems, the structures of the receptor families in each of these organs and their signaling pathways.

Reproducción y fertilidad humana: aspectos biomédicos de la familia de las lipocalinas: biología, patobiología y bioclínica / Human reproduction and fertility: biomedical aspects of the lipocalin family: biology, pathobiology and bioclinic aspects

La familia de genes de las lipocalinas (LCN) está compuesta por varios miembros que comparten una estructura común y que se han duplicado en forma repetida durante la evolución expandiéndose a más de 150 genes conocidos, de ellos al menos veinte reportados en la especie humana. El grupo de proteínas de las LCN está constituido por varios elementos que comparten la propiedad común de unión de ligandos lipofílicos. Las LCN funcionan en un amplio rango de sistemas incluyendo quimiorrecepción y transporte en fisiología sensorial del gusto y olor, coloración, modulación hemato-inmune, síntesis de prostanglandina D2, neuro-fisiología, fisiología reproductiva y fertilidad, embriogénesis, proliferación y división celular, supervivencia y apoptosis celular. Es evidente su rol en patobiología y bioclínica reproductiva y de la fertilidad al observar que varias LCN tienen niveles alterados de expresión en diferentes eventos patofisiológicos. Esta revisión resume hallazgos e implicaciones

The family of the lipocalin (LCN) genes is composed by various members that share a common structure and haveduplicated repeatedly during evolution expanding to more than 150 known genes of which at least 20 have been reported in the human species. The group of lipocalin-related proteins is comprised by a number of elements which share various common properties such as binding to different lipophilic ligands. Lipocalins are involved in a broad range of systems including chemoreception and transport functions in sensory physiology of taste and smell, coloration, modulation of hemato-immune response, synthesis of prostaglandin D2, neurophysiology, physiology of reproduction and fertility, embryogenesis, cell proliferation and division, and cell survival and apoptosis. Its role is evident in the pathophysiology and bioclinical aspects of reproduction and fertility consistent with the observation of altered levels of expression of several lipocalins in different pathophysiological events. This review summarizes findings and implications on this topic.

Study on the morphology and frequency of the vomeronasal organ in humans / Estudio sobre la morfología y la frecuencia del órgano vomeronasal en los seres humanos

The vomeronasal organ was first described in humans in the seventeenth century. It has a chemosensory function and is found in the mucosa of the nasal septum of mammals and consists of an opening in the mucosa at the base of the nasal septum. For this study, 143 individuals undergoing nasofibrolaryngoscopy were studied, and presence of the vomeronasal organ was considered to be a finding from the examination. Three morphological types of vomeronasal organ were observed: fissure, fossette and circular. The total prevalence of the vomeronasal organ among these patients was 28 percent (40 individuals ). The prevalence of the vomeronasal organ in this study population is compatible with what has been reported in other studies. The forms of the vomeronasal organ can be characterized: fissure, fossette and circular. The fossette type is commonest in males and the fissure among females.

El órgano vomeronasal se describió por primera vez en seres humanos en el siglo XVII. Tiene una función quimiosensorial y se encuentra en la mucosa del tabique nasal de los mamíferos, y consta de una abertura en la mucosa en la base del tabique nasal. Para este estudio, 143 individuos fueron estudiados mediante nasofibrolaringoscopía, y la presencia del órgano vomeronasal se consideró un hallazgo del examen. Tres tipos morfológicos de órgano vomeronasal se observaron: fisura, foseta y circular, siendo el tipo foseta es más común en los hombres y las fisuras entre las mujeres. La prevalencia total del órgano vomeronasal entre estos pacientes fue de 28 por ciento (40 pacientes). La prevalencia del órgano vomeronasal de la población en estudio es compatible con lo que ha sido reportado en otros estudios.

Androgen Receptor Distribution, PAS and Alcyan Blue Reaction in the Vomeronasal Organ and the Nasal Septum Mucosa of the Developing Male Rat / Distribución del Receptor de Andrógeno, Positividad a PAS y Alcyan Blue en el Órgano Vomeronasal y la Mucosa del Tabique Nasal Durante el Desarrollo de la Rata Macho

The vomeronasal organ (VNO) is a tubular chemoreceptory organ which detects environmental pheromones and is essential for mammalian normal reproductive activity. A sensitive chemoreceptory neuroepithelium lines the concave VNO wall and the opposite, convex wall is lined by a seudostratified, receptor-free epithelium. The secretion of the Jacobson glands (JG) -tubuloacinary glands lying in the lamina propia of the VNO - is essential for pheromones contacting vomeronasal organ chemoreceptors. Tubuloacinary glands lying in the connective tissue of the nasal septum mucosa (Bowman glands), can be classified as ventral and dorsal, according to their location. Positivity to PAS and Alcyan blue reactions and androgen receptor immunolocalization was evaluated with a semiquantitative system (0,1, 2 or 3 crosses) in JG, ventral Bowman glands (VBG), dorsal Bowman glands (DBG), sensitive chemoreceptory neuroepithelium (Ne), receptor-free epithelium (RFE) and nasal septum respiratory epithelium (RE) histological slides of male rats at 5, 15, 25 and 35 days of age. The VBG and JG were intensely positive to PAS reaction since 5 days of age, and weakly positive to Alcyan blue reaction (AB) since 15 days of age, but not at 5 days of age. Both JG and VBG were strongly positive to androgen receptor immunolocalization at all ages studied (15, 25 and 35 days of age). DBG were always negative to both PAS and AB reactions. The NE and the RFE and nasal mucosa luminar epithelium were negative. To our knowledge, this is the first report of androgen receptor (AR) immunolocalization in the vomeronasal organ and the nasal septum mucosa. The present results also suggest an influence of androgens on the mechanism of pheromones contacting with the Ne of the VNO through regulation of the Jacobson glands secretion.

El órgano vomeronasal (VNO) es un órgano quimioreceptor, tubular, que detecta feromonas ambientales. Es esencial para la actividad reproductiva normal de los mamíferos. El VNO está formado por un neuroepitelio quimiosensible (pared cóncava, Ne) y un epitelio pseudoestratificado (epitelio libre de receptores: RFE) en la pared opuesta, convexa. La secreción de las glándulas tubuloacinares de Jacobson (JG), ubicadas en la lámina propia del VNO, son esenciales para que las feromonas entren en contacto con el Ne. Las glándulas tubuloacinares ubicadas en la mucosa del tabique nasal (glándulas del Bowman), se pueden clasificar como ventrales (VBG) y dorsales (DBG), según su localization. La positividad a las técnicas de PAS, Azul de Alcián (AB) e immunolocalization del receptor de andrógeno (AR), fueron evaluadas con un sistema semicuantitativo (0, 1, 2 o 3 cruces) en láminas histológicas de JG, VBG, DBG, Ne, RFE y del epitelio del tabique nasal (RE) en ratas macho de 5, 15, 25 y 35 días de edad. Las VBG y JG fueron intensamente positivas a la reacción de PAS desde los 5 días de edad y débilmente positivas a la reacción de AB desde los 15 días de edad, pero no a los 5 días de la edad. Las JG y VBG fueron fuertemente positivas a la immunolocalization del AR en las edades estudiadas (15, 25 y 35 días de edad). Las DBG fueron siempre negativas a las reacciones de PAS y AB. El NE, el RFE y el RE fueron negativos. Según nuestro conocimiento, éste es el primer informe de immunolocalization del AR en el VNO y la mucosa del tabique nasal. Los actuales resultados sugieren una influencia de los andrógenos en el mecanismo por el cual entran en contacto las feromonas y el Ne, a través de la regulación por andrógenos de la secreción de las JG.

Histochemical Localization of NADPH-Diaphorase in the Rat Vomeronasal Organ / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The vomeronasal organ of the rat is a chemosensory organ located at the nasal septum. The distribution of nitroxidergic nerve fiber in olfactory system such as olfactory bulb, accessory olfactory bulb and olfactory epithelium was well documented, but vomeronasal organ which is a component of olfactory system and the receptor structure of the accessory olfactory system was rarely reported and discorded. The aim of this study was to determine the distribution and role of nitirc oxide (NO) in the rat vomeronasal organ using NADPH-diaphorase histochemistry. MATERIALS AND METHODS: Histochemical staining for NADPH-diaphorase in the rat vomeronasal organ was done. RESULTS: The NADPH-diaphorase positive reaction was observed in the blood vessels, nerve fibers around vessels and submucosal glands of vomeronasal organ. However, receptor area which is generally called the neuroepithelium and receptor free area were not seen. CONCLUSION: These results suggest that NADPH-diaphorase positive reaction shows tissue specific expression in the rat vomeronasal organ.