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Kotenkova E, Romachenko A, Ambaryan A, Maltsev A. Effect of early experience on neuronal and behavioral responses to con- and heterospecific odors in closely related Mus taxa: epigenetic contribution in formation of precopulatory isolation. BMC Evol Biol 2019; 19:51. [PMID: 30813903 PMCID: PMC6391773 DOI: 10.1186/s12862-019-1373-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The most effective learning occurs during sensitive periods. Olfactory plasticity to main social olfactory cues is limited to a critical period to a large degree. The objective was to evaluate the influence of early olfactory experience on the behavioral and neuronal responses of males to con- and heterospecific odors of receptive females in two species, M. musculus (subspecies musculus, wagneri) and M. spicilegus, and thus to determine the potential role of epigenetic contribution in the formation of precopulatory isolation. RESULTS Males were reciprocally cross-fostered shortly after the birth and were tested for response to con- and heterospecific urine odors of estrus females using two-choice tests at 70-85 days of age. Neuronal activity of non- and cross-fostered males was evaluated at 90-110 days of age in the MOB and AOB to con- and heterospecific female odor using fMRI (MEMRI). Non-cross-fostered males of three taxa demonstrated a strong preference for odor of conspecific females compared to odor of heterospecific ones. Spicilegus-nursed musculus preferred odor of heterospecific females. Wagneri-nursed spicilegus and spicilegus-nursed wagneri did not demonstrate significant choice of con - or heterospecific female odor. The level of MRI signal obtained from the evaluation of manganese accumulation in AOB neurons was significantly higher when the odor of conspecific estrus females was exposed, compared to urine exposure of heterospecific females. The response pattern changed to the opposite in males raised by heterospecific females. Response patterns of neuronal activity in the MOB to con- and heterospecific female odors were different in cross-fostered and control males. CONCLUSION The maternal environment, including odor, had a greater effect on the level of MRI signal in the AOB than the genetic relationships of the recipient and the donor of the odor stimulus. Behavioral and neuronal responses to con- and heterospecific odors changed in closely related Mus taxa as a result of early experience. We demonstrated the importance of early learning in mate choice in adulthood in mice and the possibility of epigenetic contribution in the formation of precopulatory reproductive isolation.
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Affiliation(s)
- Elena Kotenkova
- Severtsov Institute of Ecology and Evolution RAS, Leninsky Prospect, 33, 119071, Moscow, Russia.
| | - Alex Romachenko
- Institute of Cytology and Genetics SB RAS, Prospekt Lavrentyeva 10, 630090, Novosibirsk, Russia
| | - Alexander Ambaryan
- Severtsov Institute of Ecology and Evolution RAS, Leninsky Prospect, 33, 119071, Moscow, Russia
| | - Aleksei Maltsev
- Severtsov Institute of Ecology and Evolution RAS, Leninsky Prospect, 33, 119071, Moscow, Russia
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Licht T, Eavri R, Goshen I, Shlomai Y, Mizrahi A, Keshet E. VEGF is required for dendritogenesis of newly born olfactory bulb interneurons. Development 2010; 137:261-71. [DOI: 10.1242/dev.039636] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The angiogenic factor vascular endothelial growth factor A (VEGF) has been shown to have a role in neurogenesis, but how it affects adult neurogenesis is not fully understood. To delineate a role for VEGF in successive stages of olfactory bulb (OB) neurogenesis, we used a conditional transgenic system to suppress VEGF signaling at the adult mouse sub-ventricular zone (SVZ), rostral migratory stream (RMS) and OB, which constitute the respective sites of birth, the migration route, and sites where newly born interneurons mature and integrate within the existing OB circuitry. Following the development of fluorescently tagged adult-born neurons, we show that sequestration of VEGF that is constitutively expressed by distinct types of resident OB neurons greatly impaired dendrite development in incoming SVZ-born neurons. This was evidenced by reduced dendritic spine density of granule cells and significantly shorter and less branched dendrites in periglomerular neurons. Notably, the vasculature and perfusion of the SVZ, RMS and OB were not adversely affected when VEGF suppression was delayed until after birth, thus uncoupling the effect of VEGF on dendritogenesis from its known role in vascular maintenance. Furthermore, a requirement for VEGF was specific to newly born neurons, as already established OB neurons were not damaged by VEGF inhibition. This study thus uncovered a surprising perfusion-independent role of VEGF in the adult brain, namely, an essential role in the maturation of adult-born neurons.
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Affiliation(s)
- Tamar Licht
- Department of Molecular Biology, Hadassah Medical School, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Ronen Eavri
- Department of Molecular Biology, Hadassah Medical School, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Inbal Goshen
- Department of Molecular Biology, Hadassah Medical School, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Yael Shlomai
- Department of Neurobiology, Institute for Life Sciences, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Adi Mizrahi
- Department of Neurobiology, Institute for Life Sciences, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
| | - Eli Keshet
- Department of Molecular Biology, Hadassah Medical School, The Hebrew University of Jerusalem, 91120 Jerusalem, Israel
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Middleton FA, Carrierfenster K, Mooney SM, Youngentob SL. Gestational ethanol exposure alters the behavioral response to ethanol odor and the expression of neurotransmission genes in the olfactory bulb of adolescent rats. Brain Res 2009; 1252:105-16. [PMID: 19063871 PMCID: PMC3435114 DOI: 10.1016/j.brainres.2008.11.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Revised: 11/01/2008] [Accepted: 11/03/2008] [Indexed: 12/29/2022]
Abstract
Fetal exposure to ethanol is highly predictive of the propensity to ingest ethanol during adolescence and in utero chemosensory plasticity has been implicated as a contributing factor in this process. Recent rodent studies have shown that fetal ethanol exposure results in a tuned unconditioned sniffing and neurophysiological olfactory response to ethanol odor in infant animals. Importantly, a significant proportion of increased ethanol avidity at this age can be attributed to the tuned behavioral response to ethanol odor. These effects are absent in adults. Using behavioral methods and comprehensive gene expression profiling to screen for robust transcriptional differences induced in the olfactory bulb, we examined whether ethanol exposure via maternal diet results in an altered responsiveness to ethanol odor that persists into late adolescence and, if so, the molecular mechanisms that may be associated with such effects. Compared to controls, fetal exposure altered: the adolescent sniffing response to ethanol odor consistent with the previously observed changes in infant animals; and the expression of genes involved in synaptic transmission and plasticity as well as neuronal development (both cell fate and axon/neurite outgrowth). These data provide evidence for a persistence of olfactory-mediated responsiveness to ethanol into the period of adolescence. Further, they provide insight into an important relationship between fetal exposure to ethanol, adolescent odor responsiveness to the drug and potential underlying molecular mechanisms for the odor-guided behavioral response.
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Affiliation(s)
- Frank A. Middleton
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
- The SUNY Developmental Exposure Alcohol Research Center, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
| | - Kellyn Carrierfenster
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
- The SUNY Developmental Exposure Alcohol Research Center, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
| | - Sandra M. Mooney
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
- The SUNY Developmental Exposure Alcohol Research Center, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
| | - Steven L. Youngentob
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
- The SUNY Developmental Exposure Alcohol Research Center, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
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Thouvarecq R, Caston J, Protais P. Cholinergic system, rearing environment and trajectory learning during aging in mice. Physiol Behav 2007; 90:155-64. [PMID: 17074375 DOI: 10.1016/j.physbeh.2006.09.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 09/17/2006] [Accepted: 09/20/2006] [Indexed: 10/24/2022]
Abstract
Three, 12- and 20-month-old C57BL6/J mice, reared in standard conditions or in enriched environments, were administered subcutaneously either scopolamine hydrobromide, 0.6 or 1.2 mg kg(-1), or physiological saline (control mice) 15 min before testing their abilities to find an invisible platform in a modified version of the Morris water maze, the starting point being kept unchanged throughout the experiment to allow the aged animals to solve the task. The results demonstrated that: 1) All control mice, whatever their age, were able to learn the platform location, but the number of trials needed to reach the learning criterion (3 consecutive trials in less than 8 s) increased with age; 2) All the scopolamine-treated mice, whatever their age, were also able to learn the platform location. However, compared to age-matched controls, the number of trials needed to reach the learning criterion was greater; 3) Rearing the animals in an enriched environment antagonized the effect of scopolamine, but only in the youngest (3 month-old) mice. All control and scopolamine-treated mice, whatever their age and their rearing environment, remembered, 7 days later, the platform location.
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Affiliation(s)
- R Thouvarecq
- UPRES PSY.CO EA 1780, Faculté des Sciences, Laboratoire de Neurobiologie de l'Apprentissage, Université de Rouen, 76821 Mont-Saint-Aignan Cedex, France
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Devaud JM, Ferrús A. Molecular genetics of activity-dependent structural changes at the synapse. J Neurogenet 2004; 17:271-93. [PMID: 15204080 DOI: 10.1080/01677060390441840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Jean Marc Devaud
- Laboratoire de Génomique Fonctionelle, CNRS, UPR-2580, Montpellier, France
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Couper Leo JM, Brunjes PC. Neonatal focal denervation of the rat olfactory bulb alters cell structure and survival: a Golgi, Nissl and confocal study. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2003; 140:277-86. [PMID: 12586433 DOI: 10.1016/s0165-3806(02)00614-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Contact between sensory axons and their targets is critical for the development and maintenance of normal neural circuits. Previous work indicates that the removal of afferent contact to the olfactory bulb affects bulb organization, neurophenotypic expression, and cell survival. The studies also suggested changes to the structure of individual cell types. The current work examines the effects of denervation on the morphology of mitral/tufted, periglomerular, and granule cells. Focal denervation drastically changed mitral/tufted cell structure but had only subtle effects on periglomerular and granule cells. Denervated mitral/tufted cells lacked apical tufts and, in most cases, a primary dendrite. In addition, the denervated cells had more secondary processes whose orientation with respect to the bulb surface was altered. Our results suggest that contact between olfactory axons and the bulb is necessary for cell maintenance and may be critical for the ability of mitral/tufted cells to achieve adult morphology
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Affiliation(s)
- J M Couper Leo
- Program in Neuroscience, 102 Gilmer Hall, Box 400400, University of Virginia, Charlottesville, VA 22904-4400, USA
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Caston J, Devulder B, Jouen F, Lalonde R, Delhaye-Bouchaud N, Mariani J. Role of an enriched environment on the restoration of behavioral deficits in Lurcher mutant mice. Dev Psychobiol 1999; 35:291-303. [PMID: 10573569 DOI: 10.1002/(sici)1098-2302(199912)35:4<291::aid-dev4>3.0.co;2-u] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Lurcher mutant mice, characterized by massive degeneration of the cerebellar cortex, and normal littermate controls were reared from birth either in standard conditions or in an enriched environment. The effects of this manipulation on motor functions, landmark water maze learning, exploration, and anxiety were evaluated at 3 months of age. Under standard conditions, Lurcher mutants were impaired in comparison to controls on tests of sensorimotor function and had altered exploratory tendencies. The enriched housing improved the motor coordination of Lurcher mutants and decreased the number of trials before reaching criterion in the landmark water maze. In addition to its effects in Lurcher mutants, enriched rearing also increased some behavioral abilities in normal mice. It is hypothesized that enriched housing altered brain morphology or neurochemistry in both normal and cerebellar-damaged animals.
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Affiliation(s)
- J Caston
- Université de Rouen, Faculté des Sciences, Laboratoire de Neurobiologie de l'Apprentissage, UPRES PSY.CO 1780, 76821 Mont-Saint-Aignan Cedex, France
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Sutton JK, Brunso-Bechtold JK. Dendritic development in the dorsal lateral geniculate nucleus of ferrets in the postnatal absence of retinal input: a Golgi study. JOURNAL OF NEUROBIOLOGY 1993; 24:317-34. [PMID: 8492109 DOI: 10.1002/neu.480240305] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In order to determine the ongoing role of retinal fibers in the development of dorsal lateral geniculate nucleus (dLGN) neurons during postnatal development, the development of dLGN neurons in the postnatal absence of retinal input was studied in pigmented ferrets using the Golgi-Hortega technique. The development of four dLGN cell classes, defined on the basis of somatic and dendritic morphology, was described previously in normal ferrets (Sutton and Brunso-Bechtold, 1991, J. Comp. Neurol. 309:71-85). The present results indicate that the morphological development of dLGN neurons is strikingly similar in normal and experimental ferrets. The exuberant dendritic appendages that appear after eye opening in normal ferrets are overproduced and eliminated in the postnatal absence of retinal input; however, the final reduction of these transient appendages is delayed. Because exuberant appendages develop in the absence of retinal input, their production cannot depend upon visual experience. Differences in cell body size between normal and experimental ferrets are apparent only after neurons can be classified at the end of the first postnatal month. Cell body size is markedly reduced for class 1 neurons; class 2 cells also are reduced in size but to a far lesser extent. As there is a general trend for class 1 neurons to have the functional properties of Y-cells, it is likely that the dLGN neurons most affected by the absence of retinal input also are Y-cells.
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Affiliation(s)
- J K Sutton
- Department of Neurobiology and Anatomy, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1010
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Brunso-Bechtold JK, Henkel CK, Linville C. Ultrastructural development of the medial superior olive (MSO) in the ferret. J Comp Neurol 1992; 324:539-56. [PMID: 1430336 DOI: 10.1002/cne.903240407] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
When ferrets are born, four weeks before the onset of hearing, few synapses are evident in the medial superior olive (MSO). The synapses present are immature and almost exclusively found in the neuropil. The MSO somata are virtually devoid of synaptic contacts but are contacted by fine glial processes that increasingly ensheathe the somata during the first postnatal week. By P12, somatic synaptogenesis in the MSO is evident. Initially the terminals contain vesicles of irregular shape, size, and distribution. The glial lamellae appear to withdraw as the synaptic contacts form but continue to cover the asynaptic portions of the cell surface. The lamellae frequently extend from ensheathing the soma to encapsulate the immature terminals. During the next two weeks, synaptic density and terminal encapsulation proceed until the somata is surrounded by encapsulated synaptic terminals as in the adult ferret MSO. While most immature terminals contain round vesicles, during the first postnatal week some terminals with nonround vesicles can be distinguished. The first distinction between types of nonround vesicle-containing terminals, i.e., pleiomorphic and ovoid, is in the second postnatal week. This distinction becomes increasingly clear and by the end of the first postnatal month, terminal types can be reliably categorized. These observations indicate that: (1) synapses are present in the MSO neuropil one month prior to the onset of hearing, (2) the major period of synaptogenesis begins approximately two weeks prior to the onset of hearing, and (3) glial lamellae ensheathe MSO somata prior to the onset of somatic synaptogenesis, withdraw as synapses form, and subsequently re-extend to encapsulate newly formed synapses.
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Affiliation(s)
- J K Brunso-Bechtold
- Department of Neurobiology and Anatomy, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1010
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Sutton JK, Brunso-Bechtold JK. A Golgi study of dendritic development in the dorsal lateral geniculate nucleus of normal ferrets. J Comp Neurol 1991; 309:71-85. [PMID: 1716647 DOI: 10.1002/cne.903090106] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The development of neurons in the dorsal lateral geniculate nucleus (dLGN) of pigmented ferrets was studied by using the Golgi-Hortega technique. In adult ferrets, four dLGN cell classes were defined on the basis of somatic and dendritic morphology. Classes 1 and 2 were divided into stellate and oriented subtypes. Class 1 and 4 cells are characterized by filiform appendages, class 2 cells by club-like appendages, and class 3 cells by stalked appendages. At birth, dLGN neurons have simple dendritic arbors. During the first postnatal week, dendritic length and proximal branching density increase markedly. By postnatal day 21 (P21), dendritic morphology begins to take on mature characteristics and by the time of eye opening (P30-P35), most neurons can be classified. Also by that time, dLGN cells are covered with abundant filiform appendages. Developmental changes in appendage density were quantified for class 1 stellate cells. These data reveal that appendage density reaches a peak at P56, decreases sharply until P90, and then gradually declines to mature levels by P180. Elaboration and elimination of transient appendages occurs centrifugally; at maturity appendage density remains greater distally.
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Affiliation(s)
- J K Sutton
- Department of Neurobiology and Anatomy, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103
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Guthrie KM, Pullara JM, Marshall JF, Leon M. Olfactory deprivation increases dopamine D2 receptor density in the rat olfactory bulb. Synapse 1991; 8:61-70. [PMID: 1831300 DOI: 10.1002/syn.890080109] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Unilateral olfactory deprivation during postnatal development results in significant anatomical and neurochemical changes in the deprived olfactory bulb. Perhaps the most dramatic neurochemical change is the loss of dopaminergic expression by neurons of the glomerular region. We describe here the effects of early olfactory deprivation on other elements of the bulb dopaminergic system, namely the dopamine receptors of the olfactory bulb. Rat pups had a single naris occluded on postnatal day 2 (PN2). On PN20 or PN60, animals were sacrificed and the bulbs were examined for catecholamine levels or D2 and D1 dopamine receptor binding. Receptor densities were quantified by in vitro autoradiography using the tritiated antagonists spiperone (D2) and SCH23390 (D1). Dopamine uptake sites were similarly examined using tritiated mazindol. No significant specific labeling of D1 or mazindol sites was observed in the olfactory bulbs of control or experimental animals at either age. Normal animals displayed prominent labeling of D2 sites in the glomerular and nerve layers. After 60 days of deprivation, deprived bulbs exhibited an average increase in D2 receptor density of 32%. As determined by Scatchard analysis, the mean values for Kd and Bmax were 0.134 nM and 293 fmol/mg protein in normal bulbs, and 0.136 nM and 403 fmol/mg protein in deprived bulbs. The results suggest that, as in the neostriatum, dopamine depletion in the olfactory bulb leads to an upregulation of D2 receptor sites. This change may represent an attempt by the system to adapt neurochemically to reduced dopaminergic activity and thereby maintain bulb function.
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Affiliation(s)
- K M Guthrie
- Department of Psychobiology, University of California, Irvine 92717
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Royet JP, Jourdan F, Ploye H. Morphometric modifications associated with early sensory experience in the rat olfactory bulb: I. Volumetric study of the bulbar layers. J Comp Neurol 1989; 289:586-93. [PMID: 2592599 DOI: 10.1002/cne.902890405] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Current models of sensory coding in the olfactory bulb are based on the notion of topographical specificity in the processing of stimuli. Part of this hypothesis comes from studies of patterns of radiolabelled 2-deoxyglucose uptake, and local morphometric variations of the mitral cell size observed following prolonged exposure to an odor. The present study explored the possibility that exposing young rats to a long-term stimulation with an odor would induce spatially distributed volumetric variations of the bulbar layers. Three groups of 5 rats have been studied: (1) stimulated with ethyl acetoacetate from birth to 1 month of age, (2) unilaterally deprived following early cauterization of one nostril, and (3) normal animals of same age. Fourteen frontal histological sections uniformly distributed along the rostrocaudal axis of the olfactory bulb were used for this study. Areas of the bulbar layers were measured with the aid of an image analyser and the volume of the corresponding layers deduced by computation. Following complete sensory deprivation, the volume of all bulbar layers, except the periventricular core, was homogeneously reduced along the rostrocaudal axis of the olfactory bulb. Following long-term stimulation with ethyl acetoacetate, volume reduction was significantly higher in anterior and middle regions than in the posterior part of the olfactory bulb. It is assumed that neuronal pathways activated by ethyl acetoacetate stimulation are mainly located in the posterior part of the olfactory bulb. Functional interpretations of these results are discussed with respect to the spatial dimension in olfactory coding.
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Affiliation(s)
- J P Royet
- Laboratoire de Physiologie Neurosensorielle, ICBMC, Université Claude-Bernard, Lyon, I-CNRS, Villeurbanne, France
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Royet JP, Jourdan F, Ploye H, Souchier C. Morphometric modifications associated with early sensory experience in the rat olfactory bulb: II. Stereological study of the population of olfactory glomeruli. J Comp Neurol 1989; 289:594-609. [PMID: 2592600 DOI: 10.1002/cne.902890406] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The present study explores the local variations of size and number of olfactory glomeruli induced by the exposure of young rats to long-term stimulation with a single odor. Three groups of 5 rats were used that were either: (1) stimulated with ethyl acetoacetate from birth to 1 month of age, (2) unilaterally deprived following early occlusion of one nare, or (3) normal animals of the same age. Areas and coordinates of all glomerular profiles were measured in 14 coronal sections uniformly distributed along the rostrocaudal axis of the olfactory bulb. A distribution-free stereological method was applied to compute the size and number of glomeruli either along the bulbar rostrocaudal extent or in the bulbar coronal plane. Following complete sensory deprivation or long-term stimulation with ethyl acetoacetate, the mean diameter of glomeruli was significantly reduced everywhere, except in the ventrolateral and ventromedial regions of the posterior olfactory bulb in rats reared with a single odor. In both of these areas, the number of glomeruli was either significantly increased following long duration exposure or significantly reduced following unilateral deprivation. Thus these results show that selective modifications of the olfactory environment during postnatal maturation induce morphometric variations in specific areas of the glomerular layer. These data are discussed with respect to the concept of the topographical coding of odor quality at the level of the glomeruli and plasticity of the olfactory system during postnatal development.
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Affiliation(s)
- J P Royet
- Laboratoire de Physiologie Neurosensorielle, ICBMC, Université Claude-Bernard, Lyon, I-CNRS, Villeurbanne, France
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