The olfactory system is valuable in the study of some general properties of neural system and it provides as an excellent model for studying the effects of environmental toxicants on the sensory system. For example, the olfactory receptor neuron has become an important neurobiologic model system in the area of molecular and cell biology for the study of neuronal plasticity and neuronal development, including the developmental steps of cell birth and lineage, differentiation, synaptogenesis, migration, maturation, and death. The olfactory neuroepithelium is characteristic of neuron replacement and regeneration throughout life. Olfactory receptor neurons are rapidly replaced following traumatic lesions and they are the only known projection neurons with this property. Various toxicants put the olfactory system at risk for damage. Toxic agents comprise part of health hazard to human olfaction. However, the direct and indirect effects of these agents on the olfactory system are not completely understood.
Humans ; Neuronal Plasticity ; Neurons ; Olfactory Receptor Neurons ; Parturition ; Regeneration ; Smell

External tufted (ET) cells are the major excitatory elements coordinating the activities of glomerulars and mediating the input from the olfactory neurons to mitral cells. The ET cells participate in inter-and intra-glomerular microcircuits in the olfactory bulb, link the isofunctional odor columns within the same olfactory bulb, and play an important role in olfactory information processing. This paper reviews the research progress of the anatomy and physiological properties and electrophysiological modeling of ET cells, elaborate the problems and defects in the field. And then it further gives some proposals for the future research of electrophysiological properties, development of olfactory information coding and performance of modeling of ET cells.
Electrophysiological Phenomena ; physiology ; Humans ; Olfactory Bulb ; cytology ; physiology ; Olfactory Pathways ; physiology ; Olfactory Receptor Neurons ; cytology

Olfactory organ is an important sensory system and therefore it can serve as the research object of the neural information processing and biologic evolution due to its simplicity and ancient characteristics of the system. Besides, the olfactory biosensors based on olfactory receptor neurons (ORNs) have prosperous applications in environmental monitoring and food testing. This review introduces configuration and signal transduction of ORNs. Then it examines neuronal coding strategies and how the characteristic of responses to mechanical stimuli applied to olfactory processing. Finally, it illustrates the recent research of olfactory biosensors based on ORNs/olfactory receptors and puts forward the direction of future research.
Biosensing Techniques ; Humans ; Olfactory Perception ; physiology ; Olfactory Receptor Neurons ; physiology ; Signal Transduction ; Smell ; physiology

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

The olfactory system can detect many odorants with high sensitivity and selectivity based on the expression of nearly a thousand types of olfactory receptors (ORs) in olfactory receptor neurons (ORNs). These ORs have a dynamic odorant detection range and contribute to signal encoding processes in the olfactory bulb (OB). To harness the capabilities of the olfactory system and develop a biomimetic sensor, stable culture and maintenance of ORNs are required. However, in vitro monolayer culture models have several key limitations: i) short available period of cultured neurons, ii) low cultural efficiency, and iii) long-term storage challenges. This study aims to develop a technique: i) to support the spheroid culture of primary ORN precursors facilitating stable maintenance and long-term storage, and ii) to demonstrate the viability of ORN spheroid culture in developing an olfactory system mimetic bioelectronic nose. Recombinant protein (REP; TGPG[VGRGD(VGVPG)₆]₂₀WPC) was used to form the ORN spheroids. Spheroid formation enabled preservation of primary cultured ORNs without a significant decrease in viability or the expression of stemness markers for ten days. Physiological characteristics of the ORNs were verified by monitoring intracellular calcium concentration upon odorant mixture stimulation; response upon odorant stimulation were observed at least for ten days in these cultivated ORNs differentiated from spheroids. Coupling ORNs with multi electrode array (MEA) enabled the detection and discrimination of odorants by analyzing the electrical signal patterns generated following odorant stimulation. Taken together, the ORN spheroid culture process is a promising technique for the development of a bioelectronic nose and high-throughput odorant screening device.
Biomimetics ; Calcium ; Discrimination (Psychology) ; Electrodes ; In Vitro Techniques ; Mass Screening ; Neurons ; Nose* ; Odors ; Olfactory Bulb ; Olfactory Receptor Neurons*

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

OBJECTIVETo analyze the impact of olfactory nerve transection on the apoptosis of mice olfactory receptor neurons (ORN), and discuss the reliability of this experimental model.

METHODSAfter olfactory nerve transection of mice, anterograde horseradish peroxidase (HRP) tracing was performed to confirm the completion of nerve transection. On 8 h, 2 d, 3 d and 5 d after surgery, TdT mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) was used to observe the apoptosis of ORN, while relative semi-quantitative RT-PCR and immunohistochemistry were used to reflect the expression of olfactory marker protein (OMP, special marker of mature ORN) in olfactory epithelium.

RESULTSNo HRP label was observed in olfactory bulb after olfactory nerve transaction. Both TUNEL-positive and OMP-positive cells were ORN. After the surgery, TUNEL-positive cells increased remarkably and peaked on 2 d after the surgery. Meanwhile OMP mRNA in olfactory epithelium began to decrease markedly till 5 d after the surgery, and the olfactory epithelium got thinner accordingly.

CONCLUSIONSThis experimental model can be used reliably to sever mice olfactory nerve and manipulate simultaneous apoptosis of mice ORN.

Animals ; Apoptosis ; Denervation ; Mice ; Mice, Inbred C57BL ; Olfactory Nerve ; cytology ; metabolism ; surgery ; Olfactory Receptor Neurons ; metabolism ; pathology

Compared with other sensory system, olfactory neural system may be the most unknown one. And it is reported that the research of the complicated olfactory system is beneficial to clarifying the whole mechanism of the sensory system. Focused on spatiotemporal coding and decoding mechanism, the studies on the olfactory neural system recognition models are especially introduced. Finally, this paper presents the research work carried out in our lab, and prospects the development of this field in the future.
Computer Simulation ; Humans ; Models, Neurological ; Neural Networks (Computer) ; Olfactory Pathways ; anatomy & histology ; physiology ; Olfactory Receptor Neurons ; cytology ; 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