How keeping active pays off in the olfactory system

Although much work has investigated the contribution of brain regions such as the amygdala, hippocampus, and prefrontal cortex to the processing of fear learning and memory, fewer studies have examined the role of sensory systems, in particular the olfactory system, in the detection and perception of cues involved in learning and memory. The primary sensory receptive field maps of the olfactory system are exquisitely organized and respond dynamically to cues in the environment, remaining plastic from development through adulthood. We have previously demonstrated that olfactory fear conditioning leads to increased odorant-specific receptor representation in the main olfactory epithelium and in glomeruli within the olfactory bulb. We now demonstrate that olfactory extinction training specific to the conditioned odor stimulus reverses the conditioning-associated freezing behavior and odor learning-induced structural changes in the olfactory epithelium and olfactory bulb in an odorant ligand-specific manner. These data suggest that learning-induced freezing behavior, structural alterations, and enhanced neural sensory representation can be reversed in adult mice following extinction training.

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A Near Complete Zonal Map of Mouse Olfactory Receptors

10.1101/234187 ◽

2017 ◽

Author(s):

Longzhi Tan ◽

X. Sunney Xie

Keyword(s):

Olfactory Epithelium ◽

Olfactory System ◽

Olfactory Receptors ◽

Mrna Abundance ◽

Topological Map ◽

Main Olfactory Epithelium ◽

Regulated Expression ◽

Or Genes

AbstractIn the mouse olfactory system, spatially regulated expression of > 1,000 olfactory receptors (ORs) ― a phenomenon termed “zones” ― forms a topological map in the main olfactory epithelium (MOE). However, the zones of most ORs are currently unknown. By sequencing mRNA of 12 isolated MOE pieces, we mapped out zonal information for 1,033 OR genes with an estimated accuracy of 0.3 zones, covering 81% of all intact OR genes and 99.4% of total OR mRNA abundance. Zones tend to vary gradually along chromosomes. We further identified putative non-OR genes that may exhibit zonal expression.

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Gonadotropin Releasing Hormone (GnRH) Modulates Odorant Responses in the Peripheral Olfactory System of Axolotls

Journal of Neurophysiology ◽

10.1152/jn.01162.2002 ◽

2003 ◽

Vol 90 (2) ◽

pp. 731-738 ◽

Cited By ~ 32

Author(s):

Daesik Park ◽

Heather L. Eisthen

Keyword(s):

Glutamic Acid ◽

Olfactory Epithelium ◽

Olfactory System ◽

Gonadotropin Releasing Hormone ◽

Ambystoma Mexicanum ◽

Stimulus Interval ◽

Releasing Hormone ◽

Main Olfactory Epithelium ◽

Peripheral Olfactory System ◽

Aquatic Salamanders

Peripheral signal modulation plays an important role in sensory processing. Activity in the vertebrate olfactory epithelium may be modulated by peptides released from the terminal nerve, such as gonadotropin releasing hormone (GnRH). Here, we demonstrate that GnRH modulates odorant responses in aquatic salamanders (axolotls, Ambystoma mexicanum). We recorded electrical field potentials (electro-olfactograms, or EOGs) in response to stimulation with four different amino acid odorants, l-lysine, l-methionine, l-cysteine, and l-glutamic acid. EOG responses were recorded from the main olfactory epithelium before, during, and after application of 10 μM GnRH. This protocol was repeated for a total of three trials with 60–80 min between trials. The effect of GnRH on EOG responses was broadly similar across odorants and across trials. In general, EOG responses were reduced to 79% of the initial magnitude during application of GnRH; in some trials in which glutamic acid served as the odorant, EOG responses were enhanced during the wash period. Although the 4-min inter-stimulus interval did not lead to adaptation of EOG responses during the first trial, we frequently observed evidence of adaptation during the second and third trials. In addition, we found that lower concentrations of GnRH produced a smaller effect. These results demonstrate that GnRH can modulate odorant responses in the peripheral olfactory system.

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Faculty Opinions recommendation of A Near-Complete Spatial Map of Olfactory Receptors in the Mouse Main Olfactory Epithelium.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.733310926.793558077 ◽

2019 ◽

Author(s):

Bernd Fritzsch

Keyword(s):

Olfactory Epithelium ◽

Olfactory Receptors ◽

Main Olfactory Epithelium

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Differential and overlapping expression patterns of X-dll3 and Pax-6 genes suggest distinct roles in olfactory system development of the African clawed frog Xenopus laevis

Journal of Experimental Biology ◽

10.1242/jeb.204.12.2049 ◽

2001 ◽

Vol 204 (12) ◽

pp. 2049-2061 ◽

Cited By ~ 1

Author(s):

Marie-Dominique Franco ◽

Michael P. Pape ◽

Jennifer J. Swiergiel ◽

Gail D. Burd

Keyword(s):

Xenopus Laevis ◽

Expression Pattern ◽

Olfactory Epithelium ◽

Olfactory System ◽

De Novo ◽

System Development ◽

Expression Patterns ◽

Basal Cells ◽

Olfactory Placode ◽

Water Borne

SUMMARY In Xenopus laevis, the formation of the adult olfactory epithelium involves embryonic, larval and metamorphic phases. The olfactory epithelium in the principal cavity (PC) develops during embryogenesis from the olfactory placode and is thought to respond to water-borne odorants throughout larval life. During metamorphosis, the PC undergoes major transformations and is exposed to air-borne odorants. Also during metamorphosis, the middle cavity (MC) develops de novo. The olfactory epithelium in the MC has the same characteristics as that in the larval PC and is thought to respond to water-borne odorants. Using in situ hybridization, we analyzed the expression pattern of the homeobox genes X-dll3 and Pax-6 within the developing olfactory system. Early in development, X-dll3 is expressed in both the neuronal and non-neuronal ectoderm of the sense plate and in all cell layers of the olfactory placode and larval PC. Expression becomes restricted to the neurons and basal cells of the PC by mid-metamorphosis. During metamorphosis, X-dll3 is also expressed throughout the developing MC epithelium and becomes restricted to neurons and basal cells at metamorphic climax. This expression pattern suggests that X-dll3 is first involved in the patterning and genesis of all cells forming the olfactory tissue and is then involved in neurogenesis or neuronal maturation in putative water- and air-sensing epithelia. In contrast, Pax-6 expression is restricted to the olfactory placode, larval PC and metamorphic MC, suggesting that Pax-6 is specifically involved in the formation of water-sensing epithelium. The expression patterns suggest that X-dll3 and Pax-6 are both involved in establishing the olfactory placode during embryonic development, but subtle differences in cellular and temporal expression patterns suggest that these genes have distinct functions.

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Olfactory epithelium ontogenesis and function in postembryonic North American Bullfrog (Rana (Lithobates) catesbeiana) tadpoles

Canadian Journal of Zoology ◽

10.1139/cjz-2019-0213 ◽

2020 ◽

Vol 98 (6) ◽

pp. 367-375 ◽

Cited By ~ 1

Author(s):

J.L. Heerema ◽

S.J. Bogart ◽

C.C. Helbing ◽

G.G. Pyle

Keyword(s):

Olfactory Epithelium ◽

North American ◽

Olfactory System ◽

Postembryonic Development ◽

Acid Mixture ◽

Epithelial Surface ◽

American Bullfrog ◽

Olfactory Stimuli ◽

And Function ◽

Lithobates Catesbeiana

During metamorphosis, the olfactory system remodelling in anuran tadpoles — to transition from detecting waterborne odorants to volatile odorants as frogs — is extensive. How the olfactory system transitions from the larval to frog form is poorly understood, particularly in species that become (semi-)terrestrial. We investigated the ontogeny and function of the olfactory epithelium of North American Bullfrog (Rana (Lithobates) catesbeiana Shaw, 1802) tadpoles at various stages of postembryonic development. Changes in sensory components observable at the epithelial surface were examined by scanning electron microscopy. Functionality of the developing epithelium was tested using a neurophysiological technique (electro-olfactography (EOG)), and behaviourally, using a choice maze to assess tadpole response to olfactory stimuli (algae extract, amino acids). The youngest (premetamorphic) tadpoles responded behaviourally to an amino acid mixture despite having underdeveloped olfactory structures (cilia, olfactory knobs) and no EOG response. The consistent appearance of olfactory structures in older (prometamorphic) tadpoles coincided with reliably obtaining EOG responses to olfactory stimuli. However, as tadpoles aged further, and despite indistinguishable differences in sensory components, behavioural- and EOG-based olfactory responses were drastically reduced, most strongly near metamorphic climax. This work demonstrates a more complex relationship between structure and function of the olfactory system during tadpole life history than originally thought.

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Renewal and Differentiation of GCD Necklace Olfactory Sensory Neurons

Chemical Senses ◽

10.1093/chemse/bjaa027 ◽

2020 ◽

Vol 45 (5) ◽

pp. 333-346 ◽

Cited By ~ 1

Author(s):

Maria Lissitsyna Bloom ◽

Lucille B Johnston ◽

Sandeep Robert Datta

Keyword(s):

Sensory Neurons ◽

Olfactory Epithelium ◽

Developmental Trajectory ◽

Olfactory Sensory Neurons ◽

Differentiation Process ◽

Main Olfactory Epithelium ◽

Horizontal Migration ◽

Sensory Responses ◽

And Migration ◽

Β Tubulin

Abstract Both canonical olfactory sensory neurons (OSNs) and sensory neurons belonging to the guanylate cyclase D (GCD) “necklace” subsystem are housed in the main olfactory epithelium, which is continuously bombarded by toxins, pathogens, and debris from the outside world. Canonical OSNs address this challenge, in part, by undergoing renewal through neurogenesis; however, it is not clear whether GCD OSNs also continuously regenerate and, if so, whether newborn GCD precursors follow a similar developmental trajectory to that taken by canonical OSNs. Here, we demonstrate that GCD OSNs are born throughout adulthood and can persist in the epithelium for several months. Phosphodiesterase 2A is upregulated early in the differentiation process, followed by the sequential downregulation of β-tubulin and the upregulation of CART protein. The GCD and MS4A receptors that confer sensory responses upon GCD neurons are initially expressed midway through this process but become most highly expressed once CART levels are maximal late in GCD OSN development. GCD OSN maturation is accompanied by a horizontal migration of neurons toward the central, curved portions of the cul-de-sac regions where necklace cells are concentrated. These findings demonstrate that—like their canonical counterparts—GCD OSNs undergo continuous renewal and define a GCD-specific developmental trajectory linking neurogenesis, maturation, and migration.

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Sniffing out social signals

e-Neuroforum ◽

10.1007/s13295-010-0002-1 ◽

2010 ◽

Vol 16 (1) ◽

Cited By ~ 1

Author(s):

M. Spehr

Keyword(s):

Sexual Behavior ◽

Social Behavior ◽

Olfactory System ◽

Social Signals ◽

Specific Receptor ◽

Sensory Stimuli ◽

Main Olfactory Epithelium ◽

Sensory Structures ◽

Functionally Diverse ◽

Control Complex

AbstractIn most mammals, conspecific chemical communication strategies control complex social and sexual behavior. Just a few years ago, our concept of how the olfactory system is organized to ensure faithful transmission of social information built on the rather simplistic assumption that two fundamentally different classes of stimuli - ‘general’ odors versus ‘pheromones’ - are exclusively detected by either of two sensory structures: the main olfactory epithelium or the vomeronasal organ. A number of exciting recent findings, however, revealed a much more complex and functionally diverse organizational structure of the sense of smell. At least four anatomically segregated olfactory subsystems, some remarkably heterogeneous in their cellular composition, detect distinct, but partially overlapping populations of sensory stimuli. Discerning how subsystem-specific receptor architectures and signaling pathways orchestrate the coding logic of social chemosignals, will ultimately shed new light on the neurophysiological basis of social behavior.

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