Olfactory bulb is a critical component in encoding and processing olfactory signals, characterized by its intricate neural projections and networks dedicated to this function. It has been found that descending neural projections from the olfactory cortex and other advanced brain regions can modulate the excitability of olfactory bulb output neurons in the olfactory bulb, either directly or indirectly, which can further influence olfactory discrimination, learning, and other abilities. In recent years, advancements in optogenetic technology have facilitated extensive application of neuron manipulation for studying neural circuits, thereby greatly accelerating research into olfactory mechanisms. This review summarizes the latest research progress on the regulatory effects of neural projections from the olfactory cortex, basal forebrain, raphe nucleus, and locus coeruleus on olfactory bulb function. Furthermore, the important role that photogenetic technology plays in olfactory mechanism research is evaluated. Finally, the existing problems and future development trends in current research are preliminarily proposed and explained. This review aims to provide new insights into the mechanisms underlying olfactory neural regulation as well as applications of optogenetic technology, which are crucial for advancing the research on olfactory mechanism and the application of optogenetic technology.
Olfactory Bulb/physiology* ; Optogenetics/methods* ; Animals ; Humans ; Olfactory Pathways/physiology* ; Olfactory Cortex/physiology* ; Smell/physiology*

The study of neuronal activity with low frequency has shown an increasing interest for its greater stability and reliability recent years. One challenge in analyzing this kind of activity is to find similarities and differences between signals efficiently and effectively. The traditional analysis methods, such as short-time Fourier transform, are easily obscured by background noises and often involve a large number of parameters. Therefore, this paper introduces a novel time-frequency analysis method based on wavelet transformation and half-ellipsoid modeling to extract instantaneous frequency and instantaneous phase information. This method overcomes some shortcomings of conventional time-frequency analysis. In this method, wavelet transformation is used to provide high-level representations of raw signals, and parsimonious half-ellipsoid models are used to extract changes in time domain and frequency domain of neural recordings. The method was validated to local field potentials (LFPs) of olfactory bulb of anesthetized rats during three different odor stimuli. The results suggested that this method could detect odor-relevant features from olfactory signals with large variability. The Odors then were classified with support vector machine (SVM) algorithm and the classification accuracy reached 79.4%.
Algorithms ; Animals ; Evoked Potentials ; Fourier Analysis ; Odorants ; analysis ; Olfactory Bulb ; physiology ; Rats ; Reproducibility of Results ; Smell ; physiology ; Support Vector Machine ; Wavelet Analysis

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 ensheathing cells (OECs) are a unique type of glia with common properties of astrocyte and Schwann cells. Cultured OECs have two morphological phenotypes, astrocyte-like OECs and Schwann cell-like OECs. Reversible changes have been found between these two morphological phenotypes. However, the molecular mechanism underlying the regulation of these reversible changes is still unknown. The aim of this paper is to establish a method for the morphology plasticity of cultured OECs, and investigate the underlying mechanism. Using the primary culture of OECs and immunocytochemistry, the morphology of OECs was observed under serum, serum free media or dB-cAMP drug treatment. Statistical analysis was performed to test differences among the percentages of OEC subtypes under these conditions. The results showed that under serum free media, (95.2±3.7)% of OECs showed Schwann cell-like morphology, and (4.8±3.7)% of OECs showed astrocyte-like morphology; however, under 10% serum media, (42.5±10.4)% of OECs exhibited Schwann cell-like morphology, and (57.5±10.4)% of OECs exhibited astrocyte-like morphology. When media was changed back to serum free media for 24 h, (94.8±5.0)% of OECs showed Schwann cell-like morphology, and (5.2±5.0)% of OECs showed astrocyte-like morphology. Furthermore, culture condition with or without serum did not affect the expression of OEC cell marker, p-75 and S-100. Finally, dB-cAMP, an analog of cAMP, through inhibiting the formation of F-actin stress fibers and focal adhesion, induced the morphology switch from astrocyte-like to Schwann cell-like morphology under serum condition, promoted the branches and the growth of processes. These results suggest that serum induces the morphology plasticity of cultured OECs, which is mediated by cytoplasmic cAMP level through regulating the formation of F-actin stress fibers and focal adhesion.
Animals ; Astrocytes ; cytology ; physiology ; Cells, Cultured ; Culture Media ; pharmacology ; Cyclic AMP ; physiology ; Male ; Neuroglia ; cytology ; physiology ; Olfactory Bulb ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Schwann Cells ; cytology ; physiology ; Serum ; physiology

Extracellular recording is a key technology to study many types of brain functions. However the amplitudes of extracellular spikes are typically about 100 muV and should be picked up and amplified specially, then recorded and analyzed online. Most of the equipment for extracellular recording are either very expensive, or too large for recording in the brains of freely moving small animals. In this paper we developed a practical multi-electrode recording system based on virtual testing technology. The system includes microelectrode amplifier, analog input device NI4472 with 24-bit resolution, and data processing software SPKrec. The features of the hardware are low noise, high input impedance, a total gain of 2 000, and large dynamic range. The software developed in LabVIEW is capable of online analysis, data recording, spike detection, fire rate histograms, etc. The system functions have been verified in extracellular recording in the olfactory bulb of Gekko gecko. The result indicates that the system with performance comparable to that of commercial products meets the requirements of recording experiments.
Animals ; Brain ; physiology ; Lizards ; physiology ; Microelectrodes ; Olfactory Bulb ; physiology

BACKGROUNDImplantation of tissue-engineered scaffolds is one of the most promising therapeutic strategies for inducing nerve regenerations following spinal cord injuries. In this paper, we report a novel bioengineered hybrid scaffold comprised of three major extracellular matrix (ECM) proteins.

METHODSECM-scaffolds (ECM-S) were prepared by gelling fibrinogen, fibronectin and laminin using fresh rat plasma. Olfactory ensheathing cells (OECs) were isolated from fresh rat olfactory mucosa, purified under differential adhesion, and assessed by immunofluorescent staining. OECs were seeded onto ECM-S and cultured. The effects of the scaffolds on the seeded cells were detected using the immunofluorescent staining, Western blotting, scanning electron microscopy and transmission electron microscopy.

RESULTSTissue-engineered ECM-S could be easily molded into mat-like or cylindrical shapes and gelled by addition of fresh plasma. Observations by electron microscopy show that the ECM-S forms a stable three-dimensional porous network. Studies on the effects of the ECM-S on the biological behaviors of OECs in vitro indicate that the scaffold can promote OEC adhesion, proliferation and process extensions. Additionally, OECs seeded on the scaffold maintained the expression of nerve growth factor, matrix metalloproteinase-3 and matrix metalloproteinase-9.

CONCLUSIONWe developed a biosynthetic hybrid gel which could be used as a scaffold for OEC transplantation; this gel can promote nerve regeneration following spinal cord injuries.

Animals ; Cells, Cultured ; Immunoblotting ; Microscopy, Electron, Scanning ; Microscopy, Electron, Transmission ; Olfactory Bulb ; cytology ; physiology ; transplantation ; Olfactory Mucosa ; cytology ; physiology ; transplantation ; Rats ; Spinal Cord Injuries ; therapy ; Tissue Engineering ; methods ; Tissue Scaffolds

BACKGROUNDOlfactory ensheathing cells (OECs) can promote many kinds of neuron growth and axonal extension. The aim of the study was to investigate the effects of co-culturing with OECs on neuron apoptosis in vitro.

METHODSApoptosis was induced by treatment of cultured dorsal root ganglion neurons with 1 mmol/L hydrogen peroxide (H(2)O(2)). Cells were randomly arranged into the following treatment groups. In group 1, OECs at different density (10(4)/ml to 8 x 10(5)/ml) were added immediately after H(2)O(2) treatment and cells were co-cultured for 24 hours. In group 2, OECs were added at different time points (0, 4, 8, 12 and 24 hours) after H(2)O(2) treatment. Apoptotic cell death was determined by Hoechst 33258 staining and flow cytometry (FCM). Cell viability was determined by using methyl thiazoleterazolium (MTT) assays.

RESULTSThe results showed in the Hoechest 33258 staining, FCM and MTT that OECs have both the density-dependent protection and time-dependent protection on neuron apoptosis. The apoptosis decreased and the dorsal root ganglion neuron viability increased, when the density of OECs was increased in co-culture groups. But further increasing OEC density above 2 x 10(5)/ml (i.e. 8 x 10(5)/ml) failed to exert additional protection. As the interval between adding H(2)O(2) and adding OECs was increased, the amounts of apoptosis cells were also increased. When OECs were added 24 hours after H(2)O(2), no significant protection was observed.

CONCLUSIONThese results indicated that OECs could protect dorsal root ganglion neurons from apoptosis induced by H(2)O(2) in a density- and time-dependent manner.

Animals ; Apoptosis ; drug effects ; Cell Survival ; drug effects ; Cells, Cultured ; Coculture Techniques ; Ganglia, Spinal ; cytology ; drug effects ; Hydrogen Peroxide ; toxicity ; Male ; Olfactory Bulb ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Time Factors

Olfactory processing involves a large number of central olfactory structures, interconnected with each other in complex fashion, and incorporating both feed forward and feed back interaction. Thus understanding how these structures in odor acquisition, perception, and memory perform functional roles is a central question in olfactory disorders that can only be addressed using a combination of approaches, including neuroimaging, neurophysiology and behavioral analyses. Recent whole-brain imaging studies have shown that multiple diverse neural structures become activated during tasks involving olfactory stimulation. This article reviews the current understanding of anatomy, sensory physiology of central olfactory structures. Especially the sensory physiology of main olfactory bulb, pyriform cortex, and orbitofrontal cortex will be emphasized here.
Memory ; Neuroimaging ; Neurophysiology ; Odors ; Olfactory Bulb ; Olfactory Pathways* ; Physiology ; Smell

OBJECTIVESTo observe olfactory ensheathing glia (OEG) survival and repair in vivo for spinal cord injury after OEG transplantation.

METHODSThe OEG was cultured with the olfactory bulb of Wistar neonate rats. The spinal cords contusion was made in group A, B, and C with the New York University impactor, then complete transection was performed in the contusion area in group A. OEG labeled by Hoechst was transplanted in group A and B. In group C, DMEM were injected. In group D, laminectomies were done without cord contusion and transection. The functional recovery of the spinal cord injury [Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale scores] and changes of body weight were observed. The tissue sections were done 24 weeks postoperatively. HE staining, neurofibril (NF) immunohistochemical staining, and silver staining were performed respectively to observe the pathologic changes and axon regeneration. The survival of OEG labeled by Hoechst was observed under the fluorescence microscope.

RESULTSLocomotive behaviour improved 4 weeks postoperatively. The BBB locomotion scores of group A and B were significantly higher than that of group C in all periods (from 4 weeks to 24 weeks) (P < 0.01). Sixteen weeks after operation, the BBB locomotion scores became stable and showed no change. HE staining showed that the area of spinal cord injury was disorder and the number of nerve cell was more in group A and B. In group C, there was the obvious cavum and few wring nerve fiber in the area of spinal cord injury. The nerve fibers innervated to the injuried area in group A and B were more than that of group C, but less than that of group D. A great number of OEG labeled by Hoechst were observed around spinal injuried area under fluorescence microscope. After operation, the body weight reduced in every group. The body weight of group D had recovered after 2 weeks and gradully increased. After 4 weeks, the body weight in group A, B, and C decreased to the minimum and were significantly less than that of group D (P < 0.01). After this, body weight in group A and B increased and was significantly more than that of group C (P < 0.05).

CONCLUSIONSOEG transplantation can promote the axons regeneration and the recovery of locomotion function in experimental spinal cord injuries.

Animals ; Animals, Newborn ; Axons ; physiology ; Cells, Cultured ; Female ; Glial Fibrillary Acidic Protein ; metabolism ; Nerve Regeneration ; Neuroglia ; cytology ; transplantation ; Olfactory Bulb ; cytology ; transplantation ; Olfactory Mucosa ; cytology ; transplantation ; Rats ; Rats, Wistar ; Spinal Cord ; physiopathology ; surgery ; Spinal Cord Injuries ; surgery

OBJECTIVETo evaluate the restoration of function after spinal cord injury (SCI) in patients of different ages who have underwent intraspinal transplantation of olfactory ensheathing cells (OECs).

METHODSOne hundred and seventy-one SCI patients were included in this study. Of them, 139 were male and 32 were female, with age ranging from 2 to 64 years (mean, 34.9 years). In all SCI patients the lesions were injected at the time of operation with OECs. According to their ages, the patients were divided into 5 groups: 51 years group (n = 14). The spinal cord function was assessed based on the American Spinal Injury Association (ASIA) Classification System before and 2 - 8 weeks after OECs transplantation. One-way ANOVA and q test were used for statistical analysis, and the data were expressed as mean +/- SD.

RESULTSAfter surgery, the motor scores increased by 5.2 +/- 4.8, 8.6 +/- 8.0, 8.3 +/- 8.8, 5.7 +/- 7.3 and 8.2 +/- 7.6 in 5 age groups respectively (F = 1.009, P = 0.404); light touch scores increased by 13.9 +/- 8.1, 15.5 +/- 14.3, 12.0 +/- 14.4, 14.1 +/- 18.5 and 24.8 +/- 25.3 respectively (F = 1.837, P = 0.124); and pin prick scores increased by 11.1 +/- 7.9, 17.2 +/- 14.3, 13.2 +/- 11.8, 13.6 +/- 13.9 and 25.4 +/- 24.3 respectively (F = 2.651, P = 0.035). Restoration of pin prick in > 51 years group was better than other age groups except 21 - 30 years group.

CONCLUSIONOECs transplantation can improve the neurological function of spinal cord of SCI patients regardless of their ages. Further research into the long-term outcomes of the treatment will be required.

Adolescent ; Adult ; Age Factors ; Child ; Child, Preschool ; Female ; Humans ; Male ; Middle Aged ; Olfactory Bulb ; cytology ; transplantation ; Spinal Cord ; physiology ; Spinal Cord Injuries ; surgery ; Treatment Outcome