Mitral Cells of Olfactory Bulb Are Capable of Encoding Odor Location*

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.

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Mitral and Tufted Cells Differ in the Decoding Manner of Odor Maps in the Rat Olfactory Bulb

Journal of Neurophysiology ◽

10.1152/jn.01266.2003 ◽

2004 ◽

Vol 91 (6) ◽

pp. 2532-2540 ◽

Cited By ~ 122

Author(s):

Shin Nagayama ◽

Yuji K. Takahashi ◽

Yoshihiro Yoshihara ◽

Kensaku Mori

Keyword(s):

Olfactory Bulb ◽

Spike Activity ◽

Homologous Series ◽

Morphological Difference ◽

Aliphatic Acid ◽

Mitral Cells ◽

Firing Rates ◽

Aliphatic Acids ◽

Projection Pattern ◽

Tufted Cells

Mitral and tufted cells in the mammalian olfactory bulb are principal neurons, each type having distinct projection pattern of their dendrites and axons. The morphological difference suggests that mitral and tufted cells are functionally distinct and may process different aspects of olfactory information. To examine this possibility, we recorded odorant-evoked spike responses from mitral and middle tufted cells in the aliphatic acid- and aldehyde-responsive cluster at the dorsomedial part of the rat olfactory bulb. Homologous series of aliphatic acids and aldehydes were used for odorant stimulation. In response to adequate odorants, mitral cells showed spike responses with relatively low firing rates, whereas middle tufted cells responded with higher firing rates. Examination of the molecular receptive range (MRR) indicated that most mitral cells exhibited a robust inhibitory MRR, whereas a majority of middle tufted cells showed no or only a weak inhibitory MRR. In addition, structurally different odorants that activated neighboring clusters inhibited the spike activity of mitral cells, whereas they caused no or only a weak inhibition in the middle tufted cells. Furthermore, responses of mitral cells to an adequate excitatory odorant were greatly inhibited by mixing the odorant with other odorants that activated neighboring glomeruli. In contrast, odorants that activated neighboring glomeruli did not significantly inhibit the responses of middle tufted cells to the adequate excitatory odorant. These results indicate a clear difference between mitral and middle tufted cells in the manner of decoding the glomerular odor maps.

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Odor enrichment sculpts the abundance of olfactory bulb mitral cells

Neuroscience Letters ◽

10.1016/j.neulet.2013.02.027 ◽

2013 ◽

Vol 541 ◽

pp. 173-178 ◽

Cited By ~ 2

Author(s):

Melissa Cavallin Johnson ◽

K.C. Biju ◽

Joshua Hoffman ◽

Debra Ann Fadool

Keyword(s):

Olfactory Bulb ◽

Mitral Cells

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The Mitral and Short Axon Cells of the Olfactory Bulb

Journal of Cell Science ◽

10.1242/jcs.7.3.631 ◽

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.

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Co-localization of two-color rAAV2-retro confirms the dispersion characteristics of efferent projections of mitral cells in mouse accessory olfactory bulb

动物学研究 ◽

10.24272/j.issn.2095-8137.2020.020 ◽

2020 ◽

Vol 41 (2) ◽

pp. 148-156

Author(s):

Zheng Ning ◽

Wang Zhi-Zhong ◽

Wang Song-Wei ◽

Yang Fang-Jia ◽

Zhu Xu-Tao ◽

...

Keyword(s):

Olfactory Bulb ◽

Mitral Cells ◽

Dispersion Characteristics ◽

Accessory Olfactory Bulb ◽

Efferent Projections

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P1.1.21 Odor Discrimination by Mitral Cells in Rat Olfactory Bulb Using Microwire Array Recordinge

10.5162/imcs2012/p1.1.21 ◽

2012 ◽

Author(s):

Q. Dong ◽

J. Zhou ◽

L. J. Zhuang ◽

D. Wang ◽

P. Wang

Keyword(s):

Olfactory Bulb ◽

Odor Discrimination ◽

Mitral Cells

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An intracellular study of dendrodendritic inhibitory synapses on mitral cells in the rabbit olfactory bulb.

The Journal of Physiology ◽

10.1113/jphysiol.1978.sp012362 ◽

1978 ◽

Vol 279 (1) ◽

pp. 569-588 ◽

Cited By ~ 93

Author(s):

K Mori ◽

S F Takagi

Keyword(s):

Olfactory Bulb ◽

Inhibitory Synapses ◽

Mitral Cells ◽

Intracellular Study

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

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2020.614377 ◽

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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