The Mitral and Short Axon Cells of the Olfactory Bulb

1970 ◽  
Vol 7 (3) ◽  
pp. 631-651
Author(s):  
J. L. PRICE ◽  
T. P. S. POWELL
Keyword(s):  
Electron Microscope ◽  
Olfactory Bulb ◽  
Granule Cells ◽  
Primary Dendrite ◽  
Plexiform Layer ◽  
Mitral Cell ◽  
Granule Cell Layer ◽  
Mitral Cells ◽  
Axon Initial Segments ◽  
Large Neurons

A description is given of the mitral and short axon cells of the olfactory bulb of the rat from Golgi material examined with the light microscope and from material examined with the electron microscope. The mitral cells are large neurons with primary and secondary dendrites which both extend into the overlying external plexiform layer, although only the primary dendrite enters the glomerular formations. No predominant antero-posterior orientation of the secondary dendrites has been found. Within the glomeruli the mitral cell dendrites are in synaptic contact with the olfactory nerves and also with the periglomerular cells, but elsewhere the only synapses on the mitral cells are the ‘reciprocal synapses’ with the granule cells. Synaptic-type vesicles are found in all parts of the mitral cells, including the axon initial segments; they appear to be especially concentrated in the distal portions of the dendrites. Several types of short axon cells have been found in the granule cell layer in Golgi-impregnated material. Their cell bodies can also be distinguished with the electron microscope, and from previous work it is probable that the axons of at least some of these cells form flattened-vesicle symmetrical synapses upon the granule cells.

The Morphology of the Granule Cells of the Olfactory Bulb

1970 ◽  
Vol 7 (1) ◽  
pp. 91-123 ◽  
Author(s):  
J. L PRICE ◽  
T. P. S POWELL
Keyword(s):  
Electron Microscope ◽  
Olfactory Bulb ◽  
Cell Body ◽  
Granule Cells ◽  
Plexiform Layer ◽  
Golgi Method ◽  
Granule Cell Layer ◽  
Electron Microscopic ◽  
Microscopic Features ◽  
Large Spine

The granule cells of the olfactory bulb of the rat have been studied in material prepared by the Golgi-Kopsch method for examination with the light microscope, and in material examined with the electron microscope. With the Golgi method, the granule cells are found to have no process which can be identified as a typical axon, but from the superficial aspect of the somata stout peripheral processes arise and pass into the overlying external plexiform layer, while from the opposite side of the cell body several thinner deep dendntes extend towards the deeper parts of the bulb. Both types of processes, as well as the perikarya, have numerous spine-like appendages. On the distal portions of the peripheral processes in the external plexiform layer the appendages are much larger than on the deeper parts of the cell. The deep dendrites have localized swellings along their length which give them a varicose appearance, appendages often arise from these varicosities. The electron-microscopic features of the granule cells correspond well with the appearance of these cells in material impregnated with the Golgi method. The cell somata are small, with very little cytoplasm, and have a relatively large nucleus. The peripheral processes can be identified passing superficially from the perikarya of the granule cells; at their junction with the cell body their appearance is typically dendritic; all the cytoplasmic organelles found in the cytoplasm extend into these processes and none of the features of the initial segments of axons are found. In the external plexiform layer large spine-like appendages, which have been termed ‘gemmules’, arise from the distal portions of the peripheral processes, and participate in reciprocal synapses with the dendrites of mitral and tufted cells. The deep dendrites are much finer than the peripheral processes, and the varicosities which are seen in Golgi material may also be found with the electron microscope. Spines are found on all parts of the granule cells in the granule cell layer, including the peripheral processes, the perikarya and the deep dendrites. In addition to a spine apparatus, these spines commonly have numerous inclusions, including mitochondria, ribosomes, and vesicles which are the same size and shape as the synaptic vesicles present in the gemmules; no synapses oriented away from the spines have ever been found.

Group I Metabotropic Glutamate Receptors Are Differentially Expressed by Two Populations of Olfactory Bulb Granule Cells

2007 ◽  
Vol 97 (4) ◽  
pp. 3136-3141 ◽  
Author(s):  
Thomas Heinbockel ◽  
Kathryn A. Hamilton ◽  
Matthew Ennis
Keyword(s):  
Olfactory Bulb ◽  
Glutamate Receptors ◽  
Metabotropic Glutamate Receptors ◽  
Granule Cells ◽  
Mitral Cell ◽  
Mitral Cells ◽  
Patch Clamp Recording ◽  
Metabotropic Glutamate ◽  
Group I ◽  
Bath Application

In the main olfactory bulb, several populations of granule cells (GCs) can be distinguished based on the soma location either superficially, interspersed with mitral cells within the mitral cell layer (MCL), or deeper, within the GC layer (GCL). Little is known about the physiological properties of superficial GCs (sGCs) versus deep GCs (dGCs). Here, we used patch-clamp recording methods to explore the role of Group I metabotropic glutamate receptors (mGluRs) in regulating the activity of GCs in slices from wildtype and mGluR−/− mutant mice. In wildtype mice, bath application of the selective Group I mGluR agonist DHPG depolarized and increased the firing rate of both GC subtypes. In the presence of blockers of fast synaptic transmission (APV, CNQX, gabazine), DHPG directly depolarized both GC subtypes, although the two GC subtypes responded differentially to DHPG in mGluR1−/− and mGluR5−/− mice. DHPG depolarized sGCs in slices from mGluR5−/− mice, although it had no effect on sGCs in slices from mGluR1−/− mice. By contrast, DHPG depolarized dGCs in slices from mGluR1−/− mice but had no effect on dGCs in slices from mGluR5−/− mice. Previous studies showed that mitral cells express mGluR1 but not mGluR5. The present results therefore suggest that sGCs are more similar to mitral cells than dGCs in terms of mGluR expression.

An Electron-Microscopic Study of the Termination of the Afferent Fibres to the Olfactory Bulb from the Cerebral Hemisphere

1970 ◽  
Vol 7 (1) ◽  
pp. 157-187
Author(s):  
J. L. PRICE ◽  
T. P. S. POWELL
Keyword(s):  
Olfactory Bulb ◽  
Cerebral Hemisphere ◽  
Granule Cells ◽  
Anterior Commissure ◽  
Plexiform Layer ◽  
Granule Cell Layer ◽  
Electron Microscopic ◽  
Anterior Olfactory Nucleus ◽  
Axon Terminals ◽  
Axon Collaterals

An experimental investigation has been made of the site and mode of termination of the 3 groups of afferent fibres to the olfactory bulb which come from more caudal parts of the cerebral hemisphere. Lesions have been placed in the relevant parts of the brain of the rat and the resulting degeneration of axon terminals in the olfactory bulb studied with the electron microscope. All 3 groups of these extrinsic afferent fibres end in asymmetrical synapses upon the granule cells, and they have a differential termination upon its various processes. The possibility that these fibres also end upon other cells in the bulb (particularly the short-axon and periglomerular cells) cannot be excluded. The centrifugal fibres end upon gemmules in the deep half of the external plexiform layer only; no degenerating terminals were found in relation to the glomeruli although degenerating centrifugal axons are present here. The fibres of the anterior commissure terminate upon spines and varicosities of the deep dendrites and upon somatic spines of the granule cells. After lesions of the anterior olfactory nucleus, degenerating terminals were found in the ipsilateral olfactory bulb, which could not be ascribed to the centrifugal fibres or to the fibres of the anterior commissure, as they ended upon the spines of peripheral processes in the granule cell layer, and upon gemmules in the superficial as well as in the deep half of the external plexiform layer. It is proposed that these terminals are those of the axon collaterals from the ipsilateral anterior olfactory nucleus. The axons which form symmetrical synapses, and many which form asymmetrical synapses, do not degenerate even after a lesion immediately behind the olfactory bulb, and are therefore intrinsic to the bulb. It is suggested that the axons which are associated with symmetrical synapses are those of the short-axon cells, and the asymmetrical synapses are formed by the axon collaterals of the mitral and tufted cells.

scholarly journals Spontaneous activity generated within the olfactory bulb establishes the discrete wiring of mitral cell dendrites

2019 ◽  
Author(s):  
Satoshi Fujimoto ◽  
Marcus N. Leiwe ◽  
Richi Sakaguchi ◽  
Yuko Muroyama ◽  
Reiko Kobayakawa ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Spontaneous Activity ◽  
Neuronal Activity ◽  
Primary Dendrite ◽  
Sensory Information ◽  
Mitral Cell ◽  
Network Activity ◽  
Mitral Cells ◽  
Tufted Cells

ABSTRACTIn the mouse olfactory bulb, sensory information detected by ∼1,000 types of olfactory sensory neurons (OSNs) is represented by the glomerular map. The second-order neurons, mitral and tufted cells, connect a single primary dendrite to one glomerulus. This forms discrete connectivity between the ∼1,000 types of input and output neurons. It has remained unknown how this discrete dendrite wiring is established during development. We found that genetically silencing neuronal activity in mitral cells, but not from OSNs, perturbs the dendrite pruning of mitral cells. In vivo calcium imaging of awake neonatal animals revealed two types of spontaneous neuronal activity in mitral/tufted cells, but not in OSNs. Pharmacological and knockout experiments revealed a role for glutamate and NMDARs. The genetic blockade of neurotransmission among mitral/tufted cells reduced spontaneous activity and perturbed dendrite wiring. Thus, spontaneous network activity generated within the olfactory bulb self-organizes the parallel discrete connections in the mouse olfactory system.

scholarly journals Postnatal Developmental Expression of Calbindin, Calretinin and Parvalbumin in Mouse Main Olfactory Bulb

2005 ◽  
Vol 37 (4) ◽  
pp. 276-282 ◽  
Author(s):  
Zhao-Ping Qin ◽  
Shu-Ming Ye ◽  
Ji-Zeng Du ◽  
Gong-Yu Shen
Keyword(s):  
Olfactory Bulb ◽  
Cell Layer ◽  
Plexiform Layer ◽  
Olfactory Nerve ◽  
Mitral Cell ◽  
Granule Cell Layer ◽  
Developmental Expression ◽  
Main Olfactory Bulb ◽  
Glomerular Layer ◽  
Layer 4

Abstract The distribution of calbindin, calretinin and parvalbumin during the development of the mouse main olfactory bulb (MOB) was studied using immunohistochemistry techniques. The results are as follows: (1) calbindin-immunoreactive profiles were mainly located in the glomerular layer, and few large calbindin-immunoreactive cells were found in the subependymal layer of postnatal day 10 (P1 0) to postnatal day 40 (P40) mice; (2) no calbindin was detected in the mitral cell layer at any stage; (3) calretinin-immunoreactive profiles were present in all layers of the main olfactory bulb at all stages, especially in the olfactory nerve layer, glomerular layer and granule cell layer; (4) parvalbumin-immunoreactive profiles were mainly located in the external plexiform layer (except for P10 mice); (5) weakly stained parvalbumin-immunoreactive profiles were present in the glomerular layer at all stages; and (6) no parvalbumin was detected in the mitral cell layer at any stage.

SK Channel Regulation of Dendritic Excitability and Dendrodendritic Inhibition in the Olfactory Bulb

2005 ◽  
Vol 94 (6) ◽  
pp. 3743-3750 ◽  
Author(s):  
Brady J. Maher ◽  
Gary L. Westbrook
Keyword(s):  
Olfactory Bulb ◽  
Granule Cells ◽  
Brain Slices ◽  
Mitral Cell ◽  
Mitral Cells ◽  
Sk Channels ◽  
Action Potential Firing ◽  
Sk Channel ◽  
Dendritic Excitability ◽  
Potential Firing

Small-conductance calcium-activated potassium channels (SK) regulate dendritic excitability in many neurons. In the olfactory bulb, regulation of backpropagating action potentials and dendrodendritic inhibition depend on the dendritic excitability of mitral cells. We report here that SK channel currents are present in mitral cells but are not detectable in granule cells in the olfactory bulb. In brain slices from PND 14–21 mice, long step depolarizations (100 ms) in the mitral cell soma evoked a cadmium- and apamin-sensitive outward SK current lasting several hundred milliseconds. Block of the SK current unmasked an inward N-methyl-d-aspartate (NMDA) autoreceptor current due to glutamate released from mitral cell dendrites. In low extracellular Mg2+ (100 μM), brief step depolarizations (2 ms) evoked an apamin-sensitive current that was reduced by d,l-2-amino-5-phosphonopentanoic acid. In current- clamp, block of SK channels increased action potential firing in mitral cells as well as dendrodendritic inhibition. Our results indicate that SK channels can be activated either by calcium channels or NMDA channels in mitral cell dendrites, providing a mechanism for local control of dendritic excitability.

Synaptic Organization and Neurotransmitters in the Rat Accessory Olfactory Bulb

1999 ◽  
Vol 81 (1) ◽  
pp. 345-355 ◽  
Author(s):  
Changping Jia ◽  
Wei R. Chen ◽  
Gordon M. Shepherd
Keyword(s):  
Olfactory Bulb ◽  
Granule Cells ◽  
Mitral Cell ◽  
Activity Period ◽  
Mitral Cells ◽  
Accessory Olfactory Bulb ◽  
Field Potentials ◽  
Synaptic Organization ◽  
Evoked Field Potentials ◽  
Stimulation Of

Jia, Changping, Wei R. Chen, and Gordon M. Shepherd. Synaptic organization and neurotransmitters in the rat accessory olfactory bulb. J. Neurophysiol. 81: 345–355, 1999. The accessory olfactory bulb (AOB) is the first relay station in the vomeronasal system and may play a critical role in processing pheromone signals. The AOB shows similar but less distinct lamination compared with the main olfactory bulb (MOB). In this study, synaptic organization of the AOB was analyzed in slice preparations from adult rats by using both field potential and patch-clamp recordings. Stimulation of the vomeronasal nerve (VN) evoked field potentials that showed characteristic patterns in different layers of the AOB. Current source density (CSD) analysis of the field potentials revealed spatiotemporally separated loci of inward current (sinks) that represented sequential activation of different neuronal components: VN activity (period I), synaptic excitation of mitral cell apical dendrites (period II), and activation of granule cells by mitral cell basal dendrites (period III). Stimulation of the lateral olfactory tract also evoked field potentials in the AOB, which indicated antidromic activation of the mitral cells (period I and II) followed by activation of granule cells (period III). Whole cell patch recordings from mitral and granule cells of the AOB supported that mitral cells are excited by VN terminals and subsequently activate granule cells through dendrodendritic synapses. Both CSD analysis and patch recordings provided evidence that glutamate is the neurotransmitter at the vomeronasal receptor neuron; mitral cell synapses and both NMDA and non-NMDA receptors are involved. We also demonstrated electrophysiologically that reciprocal interaction between mitral and granule cells in the AOB is through the dendrodendritic reciprocal synapses. The neurotransmitter at the mitral-to-granule synapses is glutamate and at the granule-to-mitral synapse is γ-aminobutyric acid. The synaptic interactions among receptor cell terminals, mitral cells, and granule cells in the AOB are therefore similar to those in the MOB, suggesting that processing of chemosensory information in the AOB shares similarities with that in the MOB.

γ-Frequency Excitatory Input to Granule Cells Facilitates Dendrodendritic Inhibition in the Rat Olfactory Bulb

2003 ◽  
Vol 90 (2) ◽  
pp. 644-654 ◽  
Author(s):  
Brian Halabisky ◽  
Ben W. Strowbridge
Keyword(s):  
Olfactory Bulb ◽  
Nmda Receptors ◽  
Lateral Inhibition ◽  
Granule Cells ◽  
Critical Role ◽  
Recurrent Inhibition ◽  
Granule Cell Layer ◽  
Gabaergic Interneurons ◽  
Mitral Cells ◽  
Dendrodendritic Synapses

Recurrent and lateral inhibition play a prominent role in patterning the odor-evoked discharges in mitral cells, the output neurons of the olfactory bulb. Inhibitory responses in this brain region are mediated through reciprocal synaptic connections made between the dendrites of mitral cells and GABAergic interneurons. Previous studies have demonstrated that N-methyl-d-aspartate (NMDA) receptors on interneurons play a critical role in eliciting GABA release at reciprocal dendrodendritic synapses. In acute olfactory bulb slices, these receptors are tonically blocked by extracellular Mg2+, and recurrent inhibition is disabled. In the present study, we examined the mechanisms by which this tonic blockade could be reversed. We demonstrate that near-coincident activation of an excitatory pathway to the proximal dendrites of GABAergic interneurons relieves the Mg2+ blockade of NMDA receptors at reciprocal dendrodendritic synapses and greatly facilitates recurrent inhibition onto mitral cells. Gating of recurrent and lateral inhibition in the presence of extracellular Mg2+ requires γ-frequency stimulation of glutamatergic axons in the granule cell layer. Long-range excitatory axon connections from mitral cells innervated by different subpopulations of olfactory receptor neurons may provide a gating input to granule cells, thereby facilitating the mitral cell lateral inhibition that contributes to odorant encoding.

scholarly journals Odour discrimination in the olfactory bulb of goldfish: contrasting interactions between mitral cells and ruffed cells

2000 ◽  
Vol 355 (1401) ◽  
pp. 1229-1232 ◽  
Author(s):  
H. P. Zippel ◽  
M. Gloger ◽  
S. Nasser ◽  
S. Wilcke
Keyword(s):  
Granule Cells ◽  
Cell Activity ◽  
Plexiform Layer ◽  
Mitral Cell ◽  
Mitral Cells ◽  
Cell Potential ◽  
Tungsten Microelectrode ◽  
Odour Discrimination ◽  
Receptor Neurons ◽  
Familiar Stimuli

Anatomical differences characterizing mitral cells and ruffed cells have been published by T. Kosaka and K. Hama in three teleost species. Physiological responses from both types of relay neurons were recorded extracellularly and simultaneously in the plexiform layer, using a single tungsten microelectrode. During interstimulus intervals mitral cells responded with higher, frequently burst-like impulse rates triggered by the activity of epithelial receptor neurons. Mitral cell activity could be totally suppressed by local anaesthesia of the olfactory epithelium. Ruffed cell impulse rates were low, and each action potential triggered a long-lasting (3-5 ms), continuously varying, summed granule cell potential. During olfactory stimulation with non-familiar stimuli and important biological stimuli such as amino acids, preovulatory and ovulatory pheromones, and a probable alarm pheromone, contrasting interactions between mitral cells and ruffed cells were recorded frequently, which resulted in a drastic intensification of centrally transmitted information. An excitation of mitral cells' activity via granule cells laterally inhibited the ruffed cells' activity, and an inhibition of mitral cells' activity simultaneously ‘released’ an excitation of ruffed cells.

scholarly journals Cellular and Synaptic Mechanisms That Differentiate Mitral Cells and Superficial Tufted Cells Into Parallel Output Channels in the Olfactory Bulb

2020 ◽  
Vol 14 ◽  
Author(s):  
Shelly Jones ◽  
Joel Zylberberg ◽  
Nathan Schoppa
Keyword(s):  
Olfactory Bulb ◽  
Plexiform Layer ◽  
Input Resistance ◽  
Cell Types ◽  
Mitral Cells ◽  
Whole Cell ◽  
Wide Range ◽  
Tufted Cells ◽  
Parallel Output

A common feature of the primary processing structures of sensory systems is the presence of parallel output “channels” that convey different information about a stimulus. In the mammalian olfactory bulb, this is reflected in the mitral cells (MCs) and tufted cells (TCs) that have differing sensitivities to odors, with TCs being more sensitive than MCs. In this study, we examined potential mechanisms underlying the different responses of MCs vs. TCs. For TCs, we focused on superficial TCs (sTCs), which are a population of output TCs that reside in the superficial-most portion of the external plexiform layer, along with external tufted cells (eTCs), which are glutamatergic interneurons in the glomerular layer. Using whole-cell patch-clamp recordings in mouse bulb slices, we first measured excitatory currents in MCs, sTCs, and eTCs following olfactory sensory neuron (OSN) stimulation, separating the responses into a fast, monosynaptic component reflecting direct inputs from OSNs and a prolonged component partially reflecting eTC-mediated feedforward excitation. Responses were measured to a wide range of OSN stimulation intensities, simulating the different levels of OSN activity that would be expected to be produced by varying odor concentrations in vivo. Over a range of stimulation intensities, we found that the monosynaptic current varied significantly between the cell types, in the order of eTC > sTC > MC. The prolonged component was smaller in sTCs vs. both MCs and eTCs. sTCs also had much higher whole-cell input resistances than MCs, reflecting their smaller size and greater membrane resistivity. To evaluate how these different electrophysiological aspects contributed to spiking of the output MCs and sTCs, we used computational modeling. By exchanging the different cell properties in our modeled MCs and sTCs, we could evaluate each property's contribution to spiking differences between these cell types. This analysis suggested that the higher sensitivity of spiking in sTCs vs. MCs reflected both their larger monosynaptic OSN signal as well as their higher input resistance, while their smaller prolonged currents had a modest opposing effect. Taken together, our results indicate that both synaptic and intrinsic cellular features contribute to the production of parallel output channels in the olfactory bulb.

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