Unraveling Cajal's view of the olfactory system

Figueres-Oñate, María; Gutiérrez, Yolanda; López‐Mascaraque, Laura

doi:10.3389/fnana.2014.00055

Cited by 15 publications

(13 citation statements)

References 59 publications

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“…The OB is composed of two distinct structures: the main (MOB) and accessory olfactory bulb (AOB). Albeit sharing some common cytological organization with similarly named neurolamina -nomenclature that was carried forward from the MOB to the AOB by Ramon y Cajal (Figueres-Onate et al 2014) -there are several noteworthy differences in the organization of AOB cell types whose biophysical analyses are largely incomplete. A prominent difference lies in the principal output neurons, called mitral cells (MCs), in both systems.…”

Section: Introductionmentioning

confidence: 99%

Differential serotonergic modulation across the main and accessory olfactory bulbs

Huang

Thiebaud

Fadool

2017

The Journal of Physiology

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Mitral cells (MCs) contained in the main (MOB) and accessory (AOB) olfactory bulb have distinct intrinsic membrane properties but the extent of neuromodulation across the two systems has not been widely explored. Herein, we investigated a widely distributed CNS modulator, serotonin (5-HT), for its ability to modulate the biophysical properties of MCs across the MOB and AOB, using an in vitro, brain slice approach in postnatal 15-30 day mice. In the MOB, 5-HT elicited three types of responses in 93% of 180 cells tested. Cells were either directly excited (70%), inhibited (10%) or showed a mixed response (13%)- first inhibition followed by excitation. In the AOB, 82% of 148 cells were inhibited with 18% of cells showing no response. Albeit located in parallel partitions of the olfactory system, 5-HT largely elicited MC excitation in the MOB while it evoked two different kinetic rates of MC inhibition in the AOB. Using a combination of pharmacological agents, we found that the MC excitatory responses in the MOB were mediated by 5-HT receptors through a direct activation. In comparison, 5-HT-evoked inhibitory responses in the AOB arose due to a polysynaptic, slow-onset inhibition attributed to 5-HT receptor activation exciting GABAergic interneurons. The second type of inhibition had a rapid onset as a result of direct inhibition mediated by the 5-HT class of receptors. The distinct serotonergic modulation of MCs between the MOB and AOB could provide a molecular basis for differential chemosensory behaviours driven by the brainstem raphe nuclei into these parallel systems.

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Section: Introductionmentioning

confidence: 99%

Differential serotonergic modulation across the main and accessory olfactory bulbs

Huang

Thiebaud

Fadool

2017

The Journal of Physiology

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“…However, the linear Aβ signal could be detected in the axonal bundles between OE cells. This may be attributed to the olfactory cells being bipolar neurons which congregate to form the olfactory nerve among supporting cells . In contrast, other AD‐like mouse models exhibit different OE involvement by Aβ peptide, appearing as Aβ‐positive puncta in the basal cell layer .…”

Section: Discussionmentioning

confidence: 99%

“…This may be attributed to the olfactory cells being bipolar neurons which congregate to form the olfactory nerve among supporting cells. 19 In contrast, other AD-like mouse models exhibit different OE involvement by Aβ peptide, appearing as Aβ-positive puncta in the basal cell layer. 20 In addition, Aβ toxicity contributes to the increased apoptotic cells labeled positively with TUNEL staining in the superficial or middle layer of OE and finally lead to the atrophy of OE.…”

Section: Discussionmentioning

confidence: 99%

Olfactory dysfunction in the APP/PS1 transgenic mouse model of Alzheimer's disease: Morphological evaluations from the nose to the brain

et al. 2017

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Olfactory dysfunction is among the signs of Alzheimer's disease (AD) and cognitive impairment. It has been demonstrated Aβ was associated with olfactory impairment observed in both transgenic mice and in AD patients. In this study, we evaluated amyloid deposition in the olfactory circuit of APP/PS1 transgenic mouse model of AD, which showed olfactory dysfunction in olfactory behavior tests. We found amyloid depositions were widely distributed in the whole olfactory circuit. Moreover, we think these amyloid depositions contribute to neuronal atrophy, dendritic abnormalities, synapse loss and axonal degeneration. Therefore, there was a correlation between olfactory deficits and amyloid deposition. Our findings provide initial insights into the pathological basis of AD-related olfactory dysfunction.

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“…Figure 1 shows the structure of the rodent OB as an anatomical model for reference. Although we do not go deeper into detail in this review, there are many excellent reviews summarizing the cell types, synapses, and neuronal circuits found in the MOB ( Shepherd et al, 2004 ; Wachowiak and Shipley, 2006 ; Figueres-Onate et al, 2014 ; Imai, 2014 ; Nagayama et al, 2014 ; Sakano, 2020 ). Briefly, the OSN axons run tangentially through the olfactory nerve layer (ONL) at the surface of the OB before entering the glomerular layer (GL) ( Klenoff and Greer, 1998 ; Rodriguez-Gil et al, 2015 ).…”

Section: Basic Neural Circuitry Of the Mammalian Olfactory Systemmentioning

confidence: 99%

Subpopulations of Projection Neurons in the Olfactory Bulb

Imamura

Ito

LaFever

2020

Front. Neural Circuits

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Generation of neuronal diversity is a biological strategy widely used in the brain to process complex information. The olfactory bulb is the first relay station of olfactory information in the vertebrate central nervous system. In the olfactory bulb, axons of the olfactory sensory neurons form synapses with dendrites of projection neurons that transmit the olfactory information to the olfactory cortex. Historically, the olfactory bulb projection neurons have been classified into two populations, mitral cells and tufted cells. The somata of these cells are distinctly segregated within the layers of the olfactory bulb; the mitral cells are located in the mitral cell layer while the tufted cells are found in the external plexiform layer. Although mitral and tufted cells share many morphological, biophysical, and molecular characteristics, they differ in soma size, projection patterns of their dendrites and axons, and odor responses. In addition, tufted cells are further subclassified based on the relative depth of their somata location in the external plexiform layer. Evidence suggests that different types of tufted cells have distinct cellular properties and play different roles in olfactory information processing. Therefore, mitral and different types of tufted cells are considered as starting points for parallel pathways of olfactory information processing in the brain. Moreover, recent studies suggest that mitral cells also consist of heterogeneous subpopulations with different cellular properties despite the fact that the mitral cell layer is a single-cell layer. In this review, we first compare the morphology of projection neurons in the olfactory bulb of different vertebrate species. Next, we explore the similarities and differences among subpopulations of projection neurons in the rodent olfactory bulb. We also discuss the timing of neurogenesis as a factor for the generation of projection neuron heterogeneity in the olfactory bulb. Knowledge about the subpopulations of olfactory bulb projection neurons will contribute to a better understanding of the complex olfactory information processing in higher brain regions.

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Unraveling Cajal's view of the olfactory system

Cited by 15 publications

References 59 publications

Differential serotonergic modulation across the main and accessory olfactory bulbs

Differential serotonergic modulation across the main and accessory olfactory bulbs

Olfactory dysfunction in the APP/PS1 transgenic mouse model of Alzheimer's disease: Morphological evaluations from the nose to the brain

Subpopulations of Projection Neurons in the Olfactory Bulb

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