The Neuropil of the Glomeruli of the Olfactory Bulb

1971 ◽  
Vol 9 (2) ◽  
pp. 347-377
Author(s):  
A. J. PINCHING ◽  
T. P. S. POWELL
Keyword(s):  
Olfactory Bulb ◽  
Synaptic Contact ◽  
Axon Terminals ◽  
Large Structures ◽  
The Central Nervous System ◽  
Cellular Identity ◽  
Symmetrical Type ◽  
Spherical Vesicles ◽  
Periglomerular Cell ◽  
Periglomerular Cells

The neuropil of the glomeruli of the rat olfactory bulb has been studied with the electron microscope with a view to elucidating the type of processes involved - dendrites, appendages and axons - their cellular identity, and the synaptic relationships they establish. The problems encountered in defining these are considered and criteria based on the previous study of neuron types and on examination of serial sections are put forward. The glomeruli are large structures containing many thousands of processes and are the sole site of termination of the olfactory receptor axons. The terminals of the latter are characteristically electron-dense, allowing identification in normal material; they run through the glomeruli making many synapses by means of spherical vesicles and asymmetrical thickenings on to all types of dendritic profile. The glomerular dendritic arborizations of mitral and tufted cells, which are indistinguishable from each other, start as large, fairly regular, pale profiles but become increasingly varicose as they branch and diminish in size. They regularly show groups of spherical vesicles, often in association with asymmetrical synaptic thickenings directed from the dendrite; these are typically associated with return, reciprocal, synapses of the symmetrical type from profiles containing large flattened vesicles. These latter profiles are those of the dendrites and gemmules of periglomerular cells; the dendrites are of irregular outline and give rise to many appendages, mostly gemmules making synaptic contact with mitral or tufted cell dendrites. A small number of pale axon terminals containing either small or large flattened vesicles, derived from short-axon and periglomerular cells respectively, synapse with symmetrical thickenings on to the periglomerular cell dendritic processes. Close associations of particular types of axo-dendritic and dendro-dendritic synapses on interconnecting processes, termed synaptic patterns, are described and their significance considered. The nature of the glomerular interactions is discussed and then placed in the context of other, smaller glomeruli in the central nervous system; certain common principles of glomeruli are suggested.

The Neuropil of the Periglomerular Region of the Olfactory Bulb

1971 ◽  
Vol 9 (2) ◽  
pp. 379-409
Author(s):  
A. J. PINCHING ◽  
T. P. S. POWELL
Keyword(s):  
Olfactory Bulb ◽  
Neuronal Process ◽  
Synaptic Contacts ◽  
Axon Terminals ◽  
Cells Of Origin ◽  
Class B ◽  
Deep Layers ◽  
Tufted Cell ◽  
Spherical Vesicles ◽  
Periglomerular Cell

The periglomerular region of the olfactory bulb, apart from containing the somata and stem dendrites of the cells contributing to the glomeruli, is the sole region of distribution of the periglomerular cell thin dendrites and the short-axon cell dendrites. It is also the major site of termination of all axons to the glomerular layer except the olfactory axons - i.e. tufted cell collaterals, periglomerular cell and short-axon cell axons and centrifugal fibres. Its characteristic neuropil has been studied with the electron microscope to define the cells of origin of the types of neuronal process and their synaptic relationships. Three types of axon terminals have been found: those with spherical, large flattened and small flattened vesicles, which are deduced to derive from tufted cell collaterals or centrifugal fibres, periglomerular cell and short axon-cell axons respectively; those with spherical vesicles are consistently associated with asymmetrical membrane thickenings and those with either type of flattened vesicles with symmetrical thickenings. The thin periglomerular cell dendrites are very irregular and often have a somewhat dense cytoplasm, rich in ribosomes; they may become extended into very attenuated glia-like sheets that surround the mitral or tufted cell stem dendrites, from which they may receive synaptic contacts. Such dendrites also receive some synapses from all 3 types of axon in the periglomerular region. The short-axon cell dendrites are thick and varicose and show no sign of synaptic specialization oriented from them; they have few spines but receive many asymmetrical-type synapses on their shafts. Both axon terminal types synapsing with symmetrical thickenings are also found on the shafts. The evidence obtained from the study of normal material is summarized and the various cellular roles considered. In the light of observations on the olfactory bulb, it is suggested that dendrites may be divided into 2 major classes: those that only receive synapses (Class A) and those that make synaptic contacts as well as receiving them (Class B). Further comparisons with the deep layers of the bulb and physiological implications are discussed.

The Neuron Types of the Glomerular Layer of the Olfactory Bulb

1971 ◽  
Vol 9 (2) ◽  
pp. 305-345
Author(s):  
A. J. PINCHING ◽  
T. P. S. POWELL
Keyword(s):  
Olfactory Bulb ◽  
Structural Characteristics ◽  
Mitral Cells ◽  
Electron Microscopic ◽  
Nissl Staining ◽  
Axon Terminals ◽  
Glomerular Layer ◽  
Abundant Cytoplasm ◽  
Tufted Cells ◽  
Periglomerular Cells

The neurons of the glomerular layer of the rat olfactory bulb have been studied using Nissl staining and Golgi-Kopsch impregnation in light microscopy to define the size, shape and morphological features of individual cell somata, dendrites and axons; these have been correlated with electron-microscopic material in which fine-structural characteristics were also noted for each cell type, particularly synaptic specializations. Three neuron types are described: the external tufted and periglomerular cells of classical microscopy, and additional, superficial short-axon cells; a description of the glomerular arborizations of the mitral and deep tufted cells is also included. The tufted and mitral cells show large, non-spiny glomerular dendritic arborizations, having terminal varicosities, the external tufted cells being more limited in their branching than the deeper cells. External tufted cells have large somata and abundant cytoplasm containing stacks of Nissl material; their main dendrites are characterized by pale cytoplasm and a regular array of neurotubules. Reciprocal dendro-dendritic and somato-dendritic synapses are commonly found, the tufted/mitral cells containing spherical vesicles and contacting by means of asymmetrical membrane thickenings; the other profile involved is a gemmule containing large flattened vesicles and associated with a symmetrical thickening. The periglomerular cells are smaller, with a spiny glomerular arborization, as well as some other dendrites; all the dendrites of these cells tend to be of irregular outline. They have a dark nucleus and very little somatic cytoplasm; somatic and dendritic appendages are common and often contain large flattened vesicles. Synapses oriented from the dendritic shaft or gemmule also show such vesicles, invariably associated with symmetrical thickenings. The superficial short-axon cells are characterized by the entirely periglomerular distribution of their dendrites, which are varicose and rarely branch. Of intermediate soma dimensions, but containing dispersed Nissl material, these cells and their stem dendrites show no regions that can be designated as presynaptic. Features of axon initial segments, axo-somatic and axo-dendritic synapses are also described for each cell, as well as some unusual glial relationships. Reasons are adduced for relating the superficial short-axon cell to the axon terminal type containing small flattened vesicles, as well as for considering that the external tufted and periglomerular cells show the same synaptic specializations at their axon terminals as at their dendritic and somatic synapses. The cells of the glomerular layer are compared with those of the deeper layers of the bulb and atypical synaptic specializations discussed; some physiological implications of these findings are considered.

Uptake of Norepinephrine in Periglomerular Cells of the Olfactory Bulb of the Mouse

Nature ◽  
1966 ◽  
Vol 210 (5039) ◽  
pp. 955-956 ◽  
Author(s):  
WALTER LICHTENSTEIGER
Keyword(s):  
Olfactory Bulb ◽  
Periglomerular Cells

A Study of Terminal Degeneration in the Olfactory Bulb of the Rat

1972 ◽  
Vol 10 (3) ◽  
pp. 585-619
Author(s):  
A. J. PINCHING ◽  
T. P. S. POWELL
Keyword(s):  
Olfactory Bulb ◽  
Synaptic Cleft ◽  
Olfactory Nerve ◽  
Synaptic Membrane ◽  
Morphological Identification ◽  
Axon Terminals ◽  
Quantitative Characteristics ◽  
Terminal Degeneration ◽  
Qualitative And Quantitative Characteristics

An ultrastructural study of degeneration in axon terminals of the glomerular layer of the rat olfactory bulb is described, concentrating particularly on the sequence of degeneration in the olfactory nerve terminals and the long-term events in the degeneration process in several terminal types. Olfactory nerve terminal degeneration is divided into 5 stages, representing parts of the sequential changes taking place in the terminal after fibre section. The main features in the sequence are as follows: I. Swelling of the terminal and its vesicles. II. Initial shrinkage of the terminal, while vesicles remain swollen and some are distorted. III. Further shrinkage and darkening of the terminal, distortion of many of the vesicles and some mitochondrial swelling. IV. Extreme shrinkage of the terminal and loss of cytoplasmic detail; synaptic contact still intact or partially separated. V. Disappearance of the presynaptic terminal and persistence of the post-synaptic thickening. The validity of the observation of the persistence of post-synaptic membrane thickenings is considered and evidence adduced in its favour, both qualitative and quantitative. Characteristics of the newly apposed profiles are described, including cisternae and alveolate vesicles; the extracellular material of the synaptic cleft is considered in the light of its association with persisting thickenings. The relevance of these associated Structures is discussed in terms of function and development. Spontaneous degeneration of olfactory nerves and the degeneration of the vomeronasal nerves in the accessory olfactory bulb are described, as well as Stage V in the degeneration of other terminal types of the glomeruli, following various lesions; persistence of post-synaptic thickenings after the degeneration of terminals showing symmetrical membrane thickenings is included. Observations on the persistence of post-synaptic thickenings in various sites in the central and peripheral nervous systems are reviewed in the context of the present study; the problems arising out of the morphological identification of apposition or reinnervations are discussed.

Molecular Biology of Vertebrate Olfactory Receptors and Circuits

2021 ◽  
Author(s):  
Richard P. Tucker ◽  
Qizhi Gong
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Olfactory Bulb ◽  
Gene Family ◽  
Sensory Neuron ◽  
Sensory Neurons ◽  
Odorant Receptor ◽  
Vomeronasal Organ ◽  
Odorant Receptors ◽  
The Central Nervous System

Animals use their olfactory system for the procurement of food, the detection of danger, and the identification of potential mates. In vertebrates, the olfactory sensory neuron has a single apical dendrite that is exposed to the environment and a single basal axon that projects to the central nervous system (i.e., the olfactory bulb). The first odorant receptors to be discovered belong to an enormous gene family encoding G protein-coupled seven transmembrane domain proteins. Odorant binding to these classical odorant receptors initiates a GTP-dependent signaling cascade that uses cAMP as a second messenger. Subsequently, additional types of odorant receptors using different signaling pathways have been identified. While most olfactory sensory neurons are found in the olfactory sensory neuroepithelium, others are found in specialized olfactory subsystems. In rodents, the vomeronasal organ contains neurons that recognize pheromones, the septal organ recognizes odorant and mechanical stimuli, and the neurons of the Grüneberg ganglion are sensitive to cool temperatures and certain volatile alarm signals. Within the olfactory sensory neuroepithelium, each sensory neuron expresses a single odorant receptor gene out of the large gene family; the axons of sensory neurons expressing the same odorant receptor typically converge onto a pair of glomeruli at the periphery of the olfactory bulb. This results in the transformation of olfactory information into a spatially organized odortopic map in the olfactory bulb. The axons originating from the vomeronasal organ project to the accessory olfactory bulb, whereas the axons from neurons in the Grüneberg ganglion project to 10 specific glomeruli found in the caudal part of the olfactory bulb. Within a glomerulus, the axons originating from olfactory sensory neurons synapse on the dendrites of olfactory bulb neurons, including mitral and tufted cells. Mitral cells and tufted cells in turn project directly to higher brain centers (e.g., the piriform cortex and olfactory tubercle). The integration of olfactory information in the olfactory cortices and elsewhere in the central nervous system informs and directs animal behavior.

Olfactory Bulb

2017 ◽  
pp. 309-322
Author(s):  
Gordon M. Shepherd ◽  
Michele Migliore ◽  
Francesco Cavarretta
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Visual Cortex ◽  
Olfactory Bulb ◽  
Primary Visual Cortex ◽  
Antennal Lobe ◽  
Cell Types ◽  
Synaptic Interactions ◽  
The Central Nervous System ◽  
Olfactory Input

The olfactory bulb is the site of the first synaptic processing of the olfactory input from the nose. It is present in all vertebrates (except cetaceans) and a the analogous antennal lobe in most invertebrates. With its sharply demarcated cell types and histological layers, and some well-studied synaptic interactions, it is one of the first and clearest examples of the microcircuit concept in the central nervous system. The olfactory bulb microcircuit receives the information in the sensory domain and transforms it into information in the neural domain. Traditionally, it has been considered analogous to the retina in processing its sensory input, but that has been replaced by the view that it is more similar to the thalamus or primary visual cortex in processing its multidimensional input. This chapter describes the main synaptic connections and functional operations and how they provide the output to the olfactory cortex

scholarly journals Immunofluorescence and image analysis pipeline for Drosophila motor neurons

2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Jeremy R Brown ◽  
Chanpasith Phongthachit ◽  
Mikolaj J Sulkowski
Keyword(s):  
Image Analysis ◽  
Motor Neurons ◽  
Background Subtraction ◽  
Genetic Model ◽  
Automated Image Analysis ◽  
Ventral Ganglion ◽  
Pixel Intensity ◽  
Axon Terminals ◽  
The Central Nervous System ◽  
Motor Nuclei

Abstract The neuromuscular junction (NMJ) of larval Drosophila is widely used as a genetic model for basic neuroscience research. The presynaptic side of the NMJ is formed by axon terminals of motor neurons, the soma of which reside in the ventral ganglion of the central nervous system (CNS). Here we describe a streamlined protocol for dissection and immunostaining of the Drosophila CNS and NMJ that allows processing of multiple genotypes within a single staining tube. We also present a computer script called Automated Image Analysis with Background Subtraction which facilitates identification of motor nuclei, quantification of pixel intensity, and background subtraction. Together, these techniques provide a pipeline for neuroscientists to compare levels of different biomolecules in motor nuclei. We conclude that these methods should be adaptable to a variety of different cell and tissue types for the improvement of efficiency, reproducibility, and throughput during data quantification.

Odorant Receptors in the Formation of the Olfactory Bulb Circuitry

Physiology ◽  
2012 ◽  
Vol 27 (4) ◽  
pp. 200-212 ◽  
Author(s):  
Claudia Lodovichi ◽  
Leonardo Belluscio
Keyword(s):  
Olfactory Bulb ◽  
Axon Guidance ◽  
Sensory Neurons ◽  
Odorant Receptors ◽  
Olfactory Sensory Neurons ◽  
Neural Connectivity ◽  
Axon Terminals ◽  
Primary Function

In mammals, smell is mediated by odorant receptors expressed by sensory neurons in the nose. These specialized receptors are found both on olfactory sensory neurons' cilia and axon terminals. Although the primary function of ciliary odorant receptors is to detect odorants, their axonal role remains unclear but is thought to involve axon guidance. This review discusses findings that show axonal odorant receptors are indeed functional and capable of modulating neural connectivity.

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