Assuntos
Artérias/anatomia & histologia , Crânio/anatomia & histologia , Seio Frontal/anatomia & histologia , Seio Maxilar/anatomia & histologia , Osso Nasal/anatomia & histologia , Cavidade Nasal/anatomia & histologia , Nariz/anatomia & histologia , Órbita/anatomia & histologia , Seios Paranasais/anatomia & histologia , Conchas Nasais/anatomia & histologia , Base do Crânio/anatomia & histologia , Osso Etmoide/anatomia & histologia , Fóvea Central/anatomia & histologia , Cavidade Nasal/inervação , Cavidade Nasal/cirurgia , Septo Nasal/anatomia & histologia , Septo Nasal/inervação , Seios Paranasais/cirurgia , Seio Esfenoidal/anatomia & histologiaRESUMO
We examined the anatomy of the nasal cavity and forebrain in the axolotl (Ambystoma mexicanum) to determine whether the olfactory and vomeronasal systems are present in this neotenic aquatic salamander. The current study was motivated by two considerations: (a) little is known of the anatomy of the vomeronasal system in aquatic vertebrates, and (b) the presence of both olfactory and vomeronasal systems in larval amphibians has broad implications for the evaluation of these systems in vertebrates. From cresyl-violet-stained sections of snouts we determined that the nasal cavity of axolotls is much like that of terrestrial salamanders. The main chamber of the nasal cavity contains an olfactory epithelium, which is confined to grooves between longitudinal ridges of connective tissue covered in a nonsensory epithelium which lacks goblet cells. Using transmission electron microscopy, we found morphologically distinct olfactory receptor cells: many receptor cells terminate in microvillar dendrites, and fewer terminate in motile cilia with the 9 + 2 microtubule array typical of vertebrate olfactory receptor cells. The ciliated and microvillar cells occur in clusters with little intermingling. Horseradish peroxidase labeling revealed that axons of the olfactory receptor cells terminate in large glomeruli in the main olfactory bulb at the rostral end of the telencephalon. Lateral to the main chamber of the nasal cavity is a diverticulum that is entirely lined with a vomeronasal epithelium containing basal cells, microvillar receptor cells, sustentacular cells that lack specialized processes on the apical surface, and large ciliated cells that may function to move fluid across the vomeronasal epithelium. Unlike the olfactory epithelium, the vomeronasal epithelium lacks Bowman's glands. Using horseradish peroxidase, we determined that the axons of the vomeronasal receptor cells project to the accessory olfactory bulb, a distinct structure dorsal and caudal to the main olfactory bulb. The presence of both olfactory and vomeronasal systems in axolotls and other neotenic salamanders implies that both systems are pleiomorphic in larval amphibians; we therefore suggest that the vomeronasal system may not have originated as an adaptation to terrestrial life.
Assuntos
Ambystoma mexicanum/anatomia & histologia , Mucosa Nasal/inervação , Septo Nasal/inervação , Bulbo Olfatório/anatomia & histologia , Neurônios Receptores Olfatórios/anatomia & histologia , Prosencéfalo/anatomia & histologia , Animais , Mapeamento Encefálico , Microscopia Eletrônica , Nervo Olfatório/anatomia & histologia , Condutos Olfatórios/anatomia & histologia , Especificidade da EspécieRESUMO
In rodents the vomeronasal system plays an important role in modulating the hypothalamic control of gonadotropin secretion. It is accepted that the anatomical pathways by which the vomeronasal organ influences the neuroendocrine aspects of the reproductive behavior involves a polysynaptic system, including the accessory olfactory bulb, the 'vomeronasal amygdala', the bed nucleus of the stria terminalis and medial preoptic and ventromedial hypothalamic nuclei. We found that 72 h after unilateral transection of the vomeronasal nerves of an ipsilateral orthograde degeneration is seen in the neuropil of the medial preoptic, ventromedial, and arcuate hypothalamic nuclei. This represents an anatomical evidence of a monosynaptic link between the vomeronasal neuroepithelium and the medial preoptic nucleus, and hypothalamus.
Assuntos
Septo Nasal/inervação , Área Pré-Óptica/anatomia & histologia , Núcleo Hipotalâmico Ventromedial/anatomia & histologia , Animais , Núcleo Arqueado do Hipotálamo/anatomia & histologia , Núcleo Arqueado do Hipotálamo/fisiologia , Feminino , Histocitoquímica , Masculino , Degeneração Neural/fisiologia , Vias Neurais/anatomia & histologia , Ratos , Técnicas Estereotáxicas , Sinapses/fisiologiaRESUMO
Two technical procedures were developed in order to suppress the vomeronasal organ (V.O.) of the rat. The organ was approached through the nasal or oral cavity and electrolytic or thermic lesions were respectively performed. For electrolytic lesions the projection of the organ on the nasal bone was first determined. After opening the nasal bones, the Vs. Os. were lesioned by way of an electric current applied through an electrode introduced between the mucosa and nasal septum. For thermic lesions, the projection of the V.O. on the palate's surface was determined. After opening this area and the underlying part of the maxillary bone, both Vs. Os. were cauterized.