OBJECTIVETo study whether apoptosis plays a role in controlling the number of olfactory receptor neurons, so as to reveal the specialty and mystery of neurogenesis.

METHODSUsing terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL) and transmission electron microscopy to detect apoptosis in olfactory mucosa of normal adult rats and damaged olfactory mucosa of 16, 32, 48 hours and 3, 7, 30 days after bulbectomy.

RESULTSIn normal olfactory epithelium, a subpopulation of immature neurons, as well as mature neurons, showed internucleosomal DNA-fragmentation. The number of TUNEL-labeled neurons increased dramatically 32 hours after removal of olfactory bulb. Then it declined quickly and remained at low level. Ultrastructural data of olfactory mucosa showed that the feature of apoptotic neurons was chromatin condensation and cell shrinkage. Besides, some dying cells were characterized by the formation of numerous autophagic vacuoles, and few had some of the features of necrosis but without obvious mitochondrial swelling.

CONCLUSIONSApoptosis might play a role in turnover of the olfactory epithelium and regeneration in adult rats. There might be other two types of neural death through different mechanism.

Animals ; Apoptosis ; Male ; Olfactory Bulb ; surgery ; Olfactory Mucosa ; cytology ; pathology ; Olfactory Receptor Neurons ; cytology ; Postoperative Period ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo constitute the animal model of unilateral olfactory nerve transection and observe the expression level and distribution of odorant receptors.

METHODSThirty-two rats were divided into two groups: the olfactory nerve transection group (20) and the control group (12). The former group received the operation to transect the left olfactory nerve following the left olfactory bulb was exposed under microscope and the latter group did not give any disposal. At every stage of five days, two weeks, four weeks and six weeks after the operation, five rats from the nerve transection group and three from the control group were anaesthetized simultaneously, and olfactory epithelium were taken out after transcardial perfusion, then paraffin imbedding. Coronal sections were sliced for HE staining to observe the thickness changes of the olfactory epithelium, and for in situ hybridization (ISHs) to investigate the expression of olfactory receptor genes (Olr287, Olr226, Olr1493 and Olr1654) in the epithelium, also to evaluate the changes of the expression level and location of the selected receptors during the regeneration of olfactory epithelium.

RESULTSHE staining showed that 5 days after the operation cell quantity and thickness of the olfactory epithelium decreased obviously, which increased gradually 2 or 4 weeks after operation. After 6 weeks' recovery, the thickness of the epithelium could reach the control level. The pattern of cell staining by ISH showed a specific spatial distribution along the anteroposterior (AP) and dorsoventral (DV) axis. Evidence suggested that odorant receptors were distributed in continuous and multiple overlapping bands in the normal or nerve transected-recovered epithelium rather than in the conventionally accepted three or four zones. The data also demonstrated that the distribution of sensory neuron types, as identified and defined by odorant receptor expression, was restored to normal or nearly so by 6 weeks after operation. Likewise, the numbers of probe-labeled neurons in the nerve transected-recovered had an obvious decrease 5 days after olfactory nerve transection. Reactive cells (x(-) +/- s) of Olr1493 in the operated side was (53.9 +/- 19.9), compared with (419.0 +/- 21.2) in the unoperated side, there was statistic significance between them (t = 63.960, P < 0.01). Reactive cells increased gradually according to the regeneration of the epithelium, and were nearly equivalent to the normal side 6 weeks later without significant differentiation (t = 2.600, P > 0.05), according to the absolute positive cells in the operated and unoperated side of (417.8 +/- 32.4) and (445.3 +/- 10.0) respectively.

CONCLUSIONThe regeneration of the sensory neurons and receptors, both the number and the distribution, can recover to normal after olfactory nerve transection.

Animals ; Male ; Olfactory Mucosa ; metabolism ; Olfactory Nerve ; metabolism ; surgery ; Olfactory Nerve Injuries ; Olfactory Receptor Neurons ; cytology ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Odorant ; genetics ; metabolism

BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the effect of intranasal Mometasone furoate instillation into the nasal cavity of mice which had peripherally induced anosmia. SUBJECTS AND METHOD: Three groups of mice were studied: normal control group (nasal instillation of normal saline, n=6), Mometasone furoate non-instillation group (no treatment after nasal instillation of zinc sulfate, n=12), and Mometasone furoate instillation group (daily mometasone furoate instillation after nasal instillation of zinc sulfate, n=12). Tissues of olfactory mucosa were obtained on 1, 2, 3, 4 weeks after the instillation of zinc sulfate, and processed for immunohistochemistry using antisera to olfactory marker protein (OMP) for evaluation of olfactory regeneration. RESULTS: No OMP-positive cells were observed in the first week after the instillation of zinc sulfate in both groups. However, OMP-positive cells began appearing in the second week in both groups and gradually increased as time goes by. In the Mometasone furoate instillation group, the increase of OMP-positive cells was significantly greater than that of Mometasone furoate non-instillation group. CONCLUSION: Mometasone furoate instillation enhances regeneration of olfactory receptor cells after injury. Mometasone furoate instillation can be suggested as an effective treatment modality for olfactory dysfunction.
Animals ; Immune Sera ; Immunohistochemistry ; Mice* ; Nasal Cavity ; Olfaction Disorders ; Olfactory Marker Protein ; Olfactory Mucosa ; Olfactory Receptor Neurons ; Regeneration ; Smell ; Zinc Sulfate ; Mometasone Furoate

BACKGROUND AND OBJECTIVES: This study was undertaken to evaluate the effect of superior cervical ganglionectomy (SCG) on anosmia, which is peripherally induced in the mice. MATERIALS AND METHOD: Three groups of mice (BCF1) were studied: normal control (nasal instillation of saline, n=6); zinc sulfate group (nasal instillation of 64 mM zinc sulfate, n=25); SCG group (superior cervical ganglionectomy after nasal instillation of 64 mM zinc sulfate, n=25). Tissues of olfactory mucosa were obtained at 1, 2, 3, 4 and 7 weeks after instillation of zinc sulfate, and processed for immunohistochemistry using antisera to olfactory marker protein (OMP) to evaluate the olfactory regeneration. RESULTS: No OMP-positive cells were observed in the first two weeks after the instillation of zinc sulfate in both zinc sulfate group and the SCG group. However, the OMP-positive cells appeared first at 3 weeks after the instillation in both groups, and gradually increased in number at 4 and 7 weeks. In the SCG group, the increase of OMP-positive cells was significantly greater than those of the zinc sulfate group. The number of OMP-positive cells in the SCG group at 7 weeks was almost similar to that of the normal control group. CONCLUSION: SCG enhances regeneration of olfactory receptor cells at 3 weeks after injury. It was inferred from the above results that SCG has a significant effect on the regeneration of olfactory receptor cells and we suggest that SCG could be an effective treatment modality for olfactory dysfunction.
Animals ; Autonomic Nerve Block ; Ganglionectomy* ; Immune Sera ; Immunohistochemistry ; Mice* ; Olfaction Disorders ; Olfactory Marker Protein ; Olfactory Mucosa ; Olfactory Receptor Neurons ; Regeneration ; Smell* ; Zinc Sulfate

No abstract available.
Olfactory Mucosa*

The olfactory epithelium is the main end organ for the sense of smell in humans and vertebrates. Specially differenciated neuronal cells called olfactory receptor neurons (ORNs) play a key role in the olfactory epithelium by expressing the olfactory receptors (ORs) on their apical surface membrane. The ORs are G-protein coupled receptors that transmit signals from odorants to ORNs by molecular cascades using cyclic adenosine monophosphate, calcium ions and other molecules, which result in the depolarization of ORN. Unlike other mammalian animals, only about 30% of OR genes in the human genome are expressed. The Nobel Prize was awarded to the scientists who cloned these ORs for the first time. Each ORN expresses only a single type of OR, and ORNs which express the same type of OR converge together into the same glomeruli in the olfactory bulb. A single OR recognizes multiple odorants, and a single odorant is recognized by multiple ORs with varying affinities. At the higher neurons beyond the bulb, neuronal connections are divergent. The combinatorial model of odor identification and discrimination is well established at the convergence level, but little is known about the action mechanisms of neuronal divergence for odor identification and discrimination and further study is required.
Adenosine Monophosphate ; Animals ; Awards and Prizes ; Calcium ; Clone Cells ; Discrimination (Psychology) ; Genome, Human ; GTP-Binding Proteins ; Humans ; Ions ; Membranes ; Neurons ; Nobel Prize ; Odors ; Olfactory Bulb ; Olfactory Mucosa ; Olfactory Pathways ; Olfactory Receptor Neurons ; Receptors, Odorant ; Smell* ; Vertebrates

BACKGROUND AND OBJECTIVES: This study was performed to investigate, through immunohistochemical analysis, the thyroid hormone's effect on the olfactory receptor neurons of adult rats. MATERIALS AND METHODS: Hypothyroidism was induced by adding reversible goitrogen propylthiouracil (PTU) to the rats' drinking water (30 mg/kg weight). Sprague-Dawly rats aged nine to ten weeks were divided into three groups : control, six weeks or PTU therapy, and 12 weeks of PTU therapy. Light microscopic investigation of the olfactory mucosa was conducted with an immunohistochemical stain to observe for proliferating cell nuclear antigen (PCNA) and protein genepeptide (PGP) 9.5. RESULTS: The rats in the experimental groups gained less weight compared with normal rats of the same age. Light microscopic examination revealed no statistically significant differences in the thicknesses of the olfactory epithelium and the numbers of cells among the three groups in H-E stains, but the ratio of PCNA(+) supporting cells decreased significantly with longer durations of PTU treatment. As PTU therapy continued, immunoreactivities to PGP 9.5 in olfactory receptor cells decreased remarkably. After 12 weeks of PTU treatment, no immunoreactivity was observed in the olfactory receptor cells. CONCLUSION: These results indicate that the thyroid hormone is essential for maturation of the olfactory receptor neuron.
Adult ; Animals ; Coloring Agents ; Drinking Water ; Humans ; Hypothyroidism ; Immunohistochemistry ; Olfactory Mucosa* ; Olfactory Receptor Neurons ; Proliferating Cell Nuclear Antigen ; Propylthiouracil ; Rats* ; Thyroid Gland

OBJECTIVETo observe the microstructural changes of olfactory mucosa in rat model with acute rhinosinusitis leading to olfactory dysfunction, and to provide foundation for further exploration of corresponding mechanism.

METHODSOn the basis of prior successfully established rat model of acute rhinosinusitis through inoculation with Streptococcus pneumoniae and with the help of merocel strips, one hundred healthy SD rats were randomly divided into experimental group (80) and control group (20). After inoculation, every 20 rats in the experimental groups were sacrificed in first week, second week, third week and fourth week respectively; and all rats in the control group were sacrificed in first week after the inoculation. Before the rats were sacrificed, the method called "buffed food pellet test, BFPT" was adopted, which was advanced by professor Nathan, to measure the rats' olfaction,and the time of every rat spending in finding out the food pellet was recorded and analyzed. BFPT showed that the rats in experimental group spent (402.9 ± 9.3), (453.7 ± 7.3), (351.9 ± 8.9), (278.7 ± 8.1) s respectively in searching the food pellet, which were more than the rats in the control group [(178.3 ± 6.6) s]. Then the olfactory mucosa was collected under anatomic microscope from all the rats to make frozen section and detect the changes of mature olfactory receptor neurons (ORN) and olfactory ensheathing cells (OEC) by immunofluorescence technique.

RESULTSThe reduction of ORN in various degrees could be detected in the tissue samples of olfactory mucosa among all the rats in experimental group, with a tendency to become thinner in the thickness of epithelial lamina during the inflammation developing course. This kind of pathology was most marked in the second week and it gradually developed into the stage showing the lesion being the feeblest in the forth week following the beginning of modeling. Although the number of olfactory ensheathing cells appeared reduction in the first week following the beginning of modeling as well,it came to increase from the second week before olfactory receptor neurons and almost completely recovered to normal in the fourth week. In addition, some olfactory ensheathing cells could be detected in the tissue samples of olfactory mucosa among all the rats in experimental group.

CONCLUSIONSBoth mature olfactory sensory neurons and olfactory ensheathing cells appeared to reduction when sinonasal mucosa taken place acute rhinosinusitis. But the number of olfactory ensheathing cells increased faster than olfactory sensory neurons. In addition, some olfactory ensheathing cells could be detected in the olfactory epithelium.

Animals ; Disease Models, Animal ; Male ; Olfaction Disorders ; etiology ; pathology ; Olfactory Mucosa ; ultrastructure ; Olfactory Receptor Neurons ; Rats ; Rats, Sprague-Dawley ; Rhinitis ; pathology ; Sinusitis ; pathology ; Smell

Over the last decades, piles of data have been accumulated to understand the olfactory sensation in every aspect, ranging from the intracellular signaling to cognitive perception. This review focuses on the ion conduction through multiple ion channels expressed in olfactory sensory neurons (OSNs) to describe how odorant binding to olfactory receptors is transduced into an electrical signal. Olfactory signal transduction and the generation of the depolarizing receptor current occur in the cilia, where the unique extraciliary environment of the nasal mucosa assists in the neuronal activation. Upon contacting with odorants, OSNs dissociate G protein-coupled receptors, initiating a signal transduction pathway that leads to firing of action potential. This signaling pathway has a unique, two step organization: a cAMP-gated Ca2+ (CNG) channel and a Ca2+-activated Cl- channel (CACC), both of which contribute to signal amplification. This transduction mechanism requires an outward-directed driving force of Cl- established by active accumulation of Cl- within the lumen of the sensory cilia. To permit Cl- accumulation, OSNs avoid the expression of the 'Chloride Sensor: WNK3', that functions as the main Cl- exclusion co-transporter in neurons of the central nervous system (CNS). Cl- accumulation provides OSNs with the driving force for the depolarization, increasing the excitatory response magnitude. This is an interesting adaptation because of the fact that the olfactory cilia reside in the mucus, outside the body, where the concentrations of ions are not as well regulated as they are in normal interstitial compartments.
Action Potentials ; Central Nervous System ; Cilia ; Fires ; Ion Channels ; Ions ; Mucus ; Nasal Mucosa ; Neurons ; Odors ; Olfactory Receptor Neurons ; Sensation ; Sensory Receptor Cells* ; Signal Transduction ; Smell

No abstract available.
Animals ; Olfactory Bulb* ; Olfactory Mucosa* ; Rats* ; Synapses*