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Main Olfactory Bulb (main + olfactory_bulb)
Selected AbstractsDevelopment and topography of the lateral olfactory tract in the mouse: Imaging by genetically encoded and injected fluorescent markersDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2006Andreas Walz Abstract In mammals, conventional odorants are detected by OSNs located in the main olfactory epithelium of the nose. These neurons project their axons to glomeruli, which are specialized structures of neuropil in the olfactory bulb. Within glomeruli, axons synapse onto dendrites of projection neurons, the mitral and tufted (M/T) cells. Genetic approaches to visualize axons of OSNs expressing a given odorant receptor have proven very useful in elucidating the organization of these projections to the olfactory bulb. Much less is known about the development and connectivity of the lateral olfactory tract (LOT), which is formed by axons of M/T cells connecting the olfactory bulb to central neural regions. Here, we have extended our genetic approach to mark M/T cells of the main olfactory bulb and their axons in the mouse, by targeted insertion of IRES-tauGFP in the neurotensin locus. In NT-GFP mice, we find that M/T cells of the main olfactory bulb mature and project axons as early as embryonic day 11.5. Final innervation of central areas is accomplished before the end of the second postnatal week. M/T cell axons that originate from small defined areas within the main olfactory bulb, as visualized by localized injections of fluorescent tracers in wild-type mice at postnatal days 1 to 3, follow a dual trajectory: a branch of tightly packed axons along the dorsal aspect of the LOT, and a more diffuse branch along the ventral aspect. The dorsal, but not the ventral, subdivision of the LOT exhibits a topographical segregation of axons coming from the dorsal versus ventral main olfactory bulb. The NT-GFP mouse strain should prove useful in further studies of development and topography of the LOT, from E11.5 until 2 weeks after birth. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] A direct main olfactory bulb projection to the ,vomeronasal' amygdala in female mice selectively responds to volatile pheromones from malesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2009Ningdong Kang Abstract The main olfactory system, like the accessory olfactory system, responds to pheromones involved in social communication. Whereas pheromones detected by the accessory system are transmitted to the hypothalamus via the medial (,vomeronasal') amygdala, the pathway by which pheromones are detected and transmitted by the main system is not well understood. We examined in female mice whether a direct projection from mitral/tufted (M/T) cells in the main olfactory bulb (MOB) to the medial amygdala exists, and whether medial amygdala-projecting M/T cells are activated by volatile urinary odors from conspecifics or a predator (cat). Simultaneous anterograde tracing using Phaseolus vulgaris leucoagglutinin and Fluoro-Ruby placed in the MOB and accessory olfactory bulb (AOB), respectively, revealed that axons of MOB M/T cells projected to superficial laminae of layer Ia in anterior and posterodorsal subdivisions of the medial amygdala, whereas projection neurons from the AOB sent axons to non-overlapping, deeper layer Ia laminae of the same subdivisions. Placement of the retrograde tracer cholera toxin B into the medial amygdala labeled M/T cells that were concentrated in the ventral MOB. Urinary volatiles from male mice, but not from female conspecifics or cat, induced Fos in medial amygdala-projecting MOB M/T cells of female subjects, suggesting that information about male odors is transmitted directly from the MOB to the ,vomeronasal' amygdala. The presence of a direct MOB-to-medial amygdala pathway in mice and other mammals could enable volatile, opposite-sex pheromones to gain privileged access to diencephalic structures that control mate recognition and reproduction. [source] Cell type-dependent expression of HCN1 in the main olfactory bulbEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2003Noémi B. Holderith Abstract In many brain regions, hyperpolarization-activated cationic currents (Ih) are involved in the generation of rhythmic activities, but the role of Ih in olfactory oscillations remains unclear. Knowledge of the cellular and subcellular distributions of hyperpolarization-activated and cyclic nucleotide-gated channel (HCN) subunits is necessary for understanding the role of Ih in olfactory network activities. Using light microscopic immunocytochemistry, we demonstrate strong HCN1 labelling of the glomerular layer and moderate staining of granule cell, internal and external plexiform layers of the rat main olfactory bulb. In the glomerular layer, among many unlabelled neurons, two distinct subpopulations of juxtaglomerular cells are labelled. Approximately 10% of the juxtaglomerular cells strongly express HCN1. These small diameter cells are immunoreactive for GABA and comprise a subpopulation of periglomerular cells. An additional subset of juxtaglomerular cells (, 1%) expresses low levels of HCN1. They are large in diameter, GABA immunonegative but immunopositive for vesicular glutamate transporter 2, characterizing them as external tufted cells. Quantitative immunogold localization revealed that the somatic plasma membranes of periglomerular cells contain approximately four times more HCN1 labelling than those of external tufted cells. Unlike in cortical pyramidal cells, immunogold density for HCN1 does not significantly differ in somatic and dendritic plasma membranes of external tufted cells, indicating that post-synaptic potentials arriving at proximal and distal dendrites are modulated by the same density of Ih. Our results demonstrate a cell type-dependent expression of HCN1 in the olfactory bulb and predict a differential contribution of distinct juxtaglomerular cell types to network oscillations. [source] A novel brain receptor is expressed in a distinct population of olfactory sensory neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2000Sidonie Conzelmann Abstract Three novel G-protein-coupled receptor genes related to the previously described RA1c gene have been isolated from the mouse genome. Expression of these genes has been detected in distinct areas of the brain and also in the olfactory epithelium of the nose. Developmental studies revealed a differential onset of expression: in the brain at embryonic stage 17, in the olfactory system at stage E12. In order to determine which cell type in the olfactory epithelium expresses this unique receptor type, a transgenic approach was employed which allowed a coexpression of histological markers together with the receptor and thus visualization of the appropriate cell population. It was found that the receptor-expressing cells were located very close to the basal membrane of the epithelium; however, the cells extended a dendritic process to the epithelial surface and their axons projected into the main olfactory bulb where they converged onto two or three glomeruli in the dorsal and posterior region of the bulb. Thus, these data provide evidence that this unique type of receptor is expressed in mature olfactory neurons and suggests that it may be involved in the detection of special odour molecules. [source] Subicular and CA1 hippocampal projections to the accessory olfactory bulbHIPPOCAMPUS, Issue 2 2009C. de la Rosa-Prieto Abstract The hippocampal formation is anatomically and functionally related to the olfactory structures especially in rodents. The entorhinal cortex (EC) receives afferent projections from the main olfactory bulb; this constitutes an olfactory pathway to the hippocampus. In addition to the olfactory system, most mammals possess an accessory olfactory (or vomeronasal) system. The relationships between the hippocampal formation and the vomeronasal system are virtually unexplored. Recently, a centrifugal projection from CA1 to the accessory olfactory bulb has been identified using anterograde tracers. In the study reported herein, experiments using anterograde tracers confirm this projection, and injections of retrograde tracers show the distribution and morphology of a population of CA1 and ventral subicular neurons projecting to the accessory olfactory bulb of rats. These results extend previous descriptions of hippocampal projections to the accessory olfactory bulb by including the ventral subiculum and characterizing the morphology, neurochemistry (double labeling with somatostatin), and distribution of such neurons. These data suggest feedback hippocampal control of chemosensory stimuli in the accessory olfactory bulb. Whether this projection processes spatial information on conspecifics or is involved in learning and memory processes associated with chemical stimuli remains to be elucidated. © 2008 Wiley-Liss, Inc. [source] Changes in the connections of the main olfactory bulb after mitral cell selective neurodegenerationJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2007Javier S. Recio Abstract The connections of the main olfactory bulb (OB) of the mouse were studied with iontophoretic injections of biotinylated dextran amine. To sort efferences from mitral cells and tufted cells, the Purkinje cell degeneration (PCD) mouse was used. This mutant animal undergoes a specific neurodegeneration of mitral cells, whereas tufted cells do not degenerate. The unilateral tracer injections used were small and confined largely to the OB of both PCD and control mice at P120. Seven days after tracer injection, the efferences from the OB and the centrifugal afferences from secondary olfactory structures to it were studied. Although there is a large overlap of their target fields, mitral cell axons innervated more caudal regions of the olfactory cortex than tufted cell axons, thus providing definitive evidence of the differential projections of olfactory output neurons. Additionally, an important increase in retrogradely-labeled neurons was detected in the ipsilateral anterior olfactory nucleus of the mutant animals. This was not observed in any other secondary olfactory structure, suggesting a strengthening of the centrifugal input to the OB from that central area after mitral cell loss. Moreover, we recorded a complete loss of bilaterality in the olfactory connections of the PCD mice due to degeneration of the anterior commissure. These results point to an important reorganization of this essential olfactory circuit between the anterior olfactory nucleus and the OB, and hint at a transsynaptic level of plasticity not considered previously in literature. © 2007 Wiley-Liss, Inc. [source] General organization of the perinatal and adult accessory olfactory bulb in miceTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 9 2006Ignacio Salazar Abstract The vomeronasal system is currently a topical issue since the dual functional specificity, vomeronasal system-pheromones, has recently been questioned. Irrespective of the tools used to put such specificity in doubt, the diversity of the anatomy of the system itself in the animal kingdom is probably of more importance than has previously been considered. It has to be pointed out that a true vomeronasal system is integrated by the vomeronasal organ, the accessory olfactory bulb, and the so-called vomeronasal amygdala. Therefore, it seems reasonable to establish the corresponding differences between a well-developed vomeronasal system and other areas of the nasal cavity in which putative olfactory receptors, perhaps present in other kinds of mammals, may be able to detect pheromones and to process them. In consequence, a solid pattern for one such system in one particular species needs to be chosen. Here we report on an analysis of the general morphological characteristics of the accessory olfactory bulb in mice, a species commonly used in the study of the vomeronasal system, during growth and in adults. Our results indicate that the critical period for the formation of this structure comprises the stages between the first and the fifth day after birth, when the stratification of the bulb, the peculiarities of each type of cell, and the final building of glomeruli are completed. In addition, our data suggest that the conventional plexiform layers of the main olfactory bulb are not present in the accessory bulb. Anat Rec Part A, 288A:1009,1025, 2006. © 2006 Wiley-Liss, Inc. [source] Quantitative analysis of neuronal diversity in the mouse olfactory bulbTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2007S. Parrish-Aungst Abstract Olfactory sensory information is processed and integrated by circuits within the olfactory bulb. Golgi morphology suggests the olfactory bulb contains several major neuronal classes. However, an increasingly diverse collection of neurochemical markers have been localized in subpopulations of olfactory bulb neurons. While the mouse is becoming the animal model of choice for olfactory research, little is known about the proportions of neurons expressing and coexpressing different neurochemical markers in this species. Here we characterize neuronal populations in the mouse main olfactory bulb, focusing on glomerular populations. Immunofluorescent labeling for: 1) calretinin, 2) calbindin D-28K (CB), 3) parvalbumin, 4) neurocalcin, 5) tyrosine hydroxylase (TH), 6) the 67-kDa isoform of GAD (GAD67), and 7) the neuronal marker NeuN was performed in mice expressing green fluorescent protein under the control of the glutamic acid decarboxylase 65kDa (GAD65) promoter. Using unbiased stereological cell counts we estimated the total numbers of cells and neurons in the bulb and the number and percentage of neurons expressing and coexpressing different neurochemical populations in each layer of the olfactory bulb. Use of a genetic label for GAD65 and immunohistochemistry for GAD67 identified a much larger percentage of GABAergic neurons in the glomerular layer (55% of all neurons) than previously recognized. Additionally, while many glomerular neurons expressing TH or CB coexpress GAD, the majority of these neurons preferentially express the GAD67 isoform. These data suggest that the chemospecific populations of neurons in glomeruli form distinct subpopulations and that GAD isoforms are preferentially regulated in different neurochemical cell types. J. Comp. Neurol. 501:825,836, 2007. © 2007 Wiley-Liss, Inc. [source] Differential responses to branched and unsaturated aliphatic hydrocarbons in the rat olfactory systemTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2006Sabrina L. Ho Abstract In an effort to understand mammalian olfactory processing, we have been describing the responses to systematically different odorants in the glomerular layer of the main olfactory bulb of rats. Previously, we demonstrated chemotopically organized and distinct olfactory responses to a homologous series of straight-chained alkanes that consisted of purely hydrocarbon structures, indicating that hydrocarbon chains could serve as molecular features in the combinatorial coding of odorant information. To better understand the processing of hydrocarbon odorants, we now have examined responses to other types of chemical changes in these kinds of molecules, namely, branching and carbon,carbon bond saturation. To this end, we used the [14C]2-deoxyglucose method to determine glomerular responses to a group of eight-carbon branched alkane isomers, unsaturated octenes (double-bonded), and octynes (triple-bonded). In contrast to the differential responses we observed previously for straight-chained alkanes of differing carbon number, the rat olfactory system was not particularly sensitive to these variations in branching and bond saturation. This result was unexpected, given the distinct molecular conformations and property profiles of the odorants. The similarity in activity patterns was paralleled by a similarity in spontaneous perceptual responses measured using a habituation assay. These results demonstrate again the functional relationship between bulbar activity patterns and odor perception. The results further suggest that the olfactory system does not respond equally to all aspects of odorant chemistry, functioning as a specific, rather than a general, chemical analysis system. J. Comp. Neurol. 499:519,532, 2006. © 2006 Wiley-Liss, Inc. [source] Laminar organization of the developing lateral olfactory tract revealed by differential expression of cell recognition moleculesTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2004Koichiro Inaki Abstract The projection neurons in the olfactory bulb (mitral and tufted cells) send axons through the lateral olfactory tract (LOT) onto several structures of the olfactory cortex. However, little is known of the molecular and cellular mechanisms underlying establishment of functional connectivity from the bulb to the cortex. Here, we investigated the developmental process of LOT formation by observing expression patterns of cell recognition molecules in embryonic mice. We immunohistochemically identified a dozen molecules expressed in the developing LOT and some of them were localized to subsets of mitral cell axons. Combinatorial immunostaining for these molecules revealed that the developing LOT consists of three laminas: superficial, middle, and deep. Detailed immunohistochemical, in situ hybridization, and 5-bromodeoxyuridine labeling analyses suggested that the laminar organization reflects: 1) the segregated pathways from the accessory and main olfactory bulbs, and 2) the different maturity of mitral cell axons. Mitral cell axons of the accessory olfactory bulb were localized to the deep lamina, segregated from those of the main olfactory bulb. In the main olfactory pathway, axons of mature mitral cells, whose somata is located in the apical sublayer of the mitral cell layer, were localized to the middle lamina within LOT, while those of immature mitral cells that located in the basal sublayer were complementarily localized to the superficial lamina. These results suggest that newly generated immature axons are added to the most superficial lamina of LOT successively, leading to the formation of piled laminas with different maturational stages of the mitral cell axons. J. Comp. Neurol. 479:243,256, 2004. © 2004 Wiley-Liss, Inc. [source] Localization and connectivity of the lateral amygdala in anuran amphibiansTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2004Nerea Moreno Abstract On the basis of chemoarchitecture and gene expression patterns in the amphibian amygdaloid complex, new subdivisions have been proposed and compared with their counterparts in amniotes. Thus, a portion of the ventral pallium of anurans has been tentatively named "lateral amygdala" (LA) and compared with the basolateral complex of mammals. To strengthen the putative homology, we have analyzed the pattern of afferent and efferent connections of the LA in the anurans Rana perezi and Xenopus laevis. Tract-tracing techniques with dextran amines were used under in vivo and in vitro conditions. The results showed important connections with the main olfactory bulb, via the lateral olfactory tract. In addition, abundant intratelencephalic connections, via the rostral branch of the stria terminalis, were revealed, involving mainly the basal ganglia, septal nuclei, bed nucleus of the stria terminalis, and especially other amygdaloid nuclei. Nontelencephalic connections were found from the dorsal thalamus and parabrachial area and, in particular, from the hypothalamus through the caudal branch of the stria terminalis. All these results strongly suggest that the LA in anurans is a multimodal area in the ventral pallium that shares many hodological features with the amygdaloid ventropallial derivatives of the basolateral complex of amniotes. J. Comp. Neurol. 479:130,148, 2004. © 2004 Wiley-Liss, Inc. [source] Structure of intraglomerular dendritic tufts of mitral cells and their contacts with olfactory nerve terminals and calbindin-immunoreactive type 2 periglomerular neuronsTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2001Katsuko Kosaka Abstract Intraglomerular dendritic tufts of Golgi-impregnated and biotinylated dextran amine (BDA)-labeled mitral cells in the rat main olfactory bulb were analyzed in detail. In particular, the relationships of BDA-labeled tufts with olfactory nerve (ON) terminals and processes of calbindin D-28K-immunoreactive (CB-IR) cells were investigated with confocal laser-scanning light microscopic (CLSM) and electron microscopic (EM) analyses. CB-IR cells were type 2 periglomerular cells that restricted their processes in the ON-free (non-ON) zone of the glomerulus and received few synapses from ON terminals. The mitral tufts varied in complexity, but individual branches were rather simple, smooth processes that bore some branchlets and spines and extended more or less in a straight line or a gentle curve rather than winding tortuously within glomeruli as though they did not consider the compartmental organization, which consisted of ON and non-ON zones that interdigitated in a complex manner with one another. Conventional EM analysis revealed that both thin and thick, presumed proximal branches of mitral/tufted cell dendritic tufts received asymmetrical synapses from ON terminals. Correlated CLSM-EM analysis confirmed direct contacts between the BDA- and CB-labeled processes detected in the CLSM examinations, and synapses were recognized at some of those sites. Furthermore, ON terminals and CB-IR processes were distributed on both proximal and distal dendritic branches in a more or less mosaic pattern. These findings revealed that, on the mitral dendritic tufts, ON terminals and processes of type 2 periglomerular neurons were not clearly segregated proximodistally but, rather, were arranged in a mosaic pattern, which may be important in fine tuning the output from individual glomeruli. J. Comp. Neurol. 440:219,235, 2001. © 2001 Wiley-Liss, Inc. [source] Laminar organization of the developing lateral olfactory tract revealed by differential expression of cell recognition moleculesTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2004Koichiro Inaki Abstract The projection neurons in the olfactory bulb (mitral and tufted cells) send axons through the lateral olfactory tract (LOT) onto several structures of the olfactory cortex. However, little is known of the molecular and cellular mechanisms underlying establishment of functional connectivity from the bulb to the cortex. Here, we investigated the developmental process of LOT formation by observing expression patterns of cell recognition molecules in embryonic mice. We immunohistochemically identified a dozen molecules expressed in the developing LOT and some of them were localized to subsets of mitral cell axons. Combinatorial immunostaining for these molecules revealed that the developing LOT consists of three laminas: superficial, middle, and deep. Detailed immunohistochemical, in situ hybridization, and 5-bromodeoxyuridine labeling analyses suggested that the laminar organization reflects: 1) the segregated pathways from the accessory and main olfactory bulbs, and 2) the different maturity of mitral cell axons. Mitral cell axons of the accessory olfactory bulb were localized to the deep lamina, segregated from those of the main olfactory bulb. In the main olfactory pathway, axons of mature mitral cells, whose somata is located in the apical sublayer of the mitral cell layer, were localized to the middle lamina within LOT, while those of immature mitral cells that located in the basal sublayer were complementarily localized to the superficial lamina. These results suggest that newly generated immature axons are added to the most superficial lamina of LOT successively, leading to the formation of piled laminas with different maturational stages of the mitral cell axons. J. Comp. Neurol. 479:243,256, 2004. © 2004 Wiley-Liss, Inc. [source] Organization of the main olfactory bulbs of some mammals: Musk shrews, moles, hedgehogs, tree shrews, bats, mice, and ratsTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2004Katsuko Kosaka Abstract We immunohistochemically examined the organization of the main olfactory bulbs (MOBs) in seven mammalian species, including moles, hedgehogs, tree shrews, bats, and mice as well as laboratory musk shrews and rats. We focused our investigation on two points: 1) whether nidi, particular spheroidal synaptic regions subjacent to glomeruli, which we previously reported for the laboratory musk shrew MOBs, are also present in other animals and 2) whether the compartmental organization of glomeruli and two types of periglomerular cells we proposed for the rat MOBs are general in other animals. The general laminar pattern was similar among these seven species, but discrete nidi and the nidal layer were recognized only in two insectivores, namely, the mole and laboratory musk shrew. Olfactory marker protein-immunoreactive (OMP-IR) axons extended beyond the limits of the glomerular layer (GL) into the superficial region of the external plexiform layer (EPL) or the nidal layer in the laboratory musk shrew, mole, hedgehog, and tree shrew but not in bat, mouse, and rat. We observed, in nidi and the nidal layer in the mole and laboratory musk shrew MOBs, only a few OMP-IR axons. In the hedgehog, another insectivore, OMP-IR processes extending from the glomeruli were scattered and intermingled with calbindin D28k-IR cells at the border between the GL and the EPL. In the superficial region of the EPL of the tree shrew MOBs, there were a small number of tiny glomerulus-like spheroidal structures where OMP-IR axons protruding from glomeruli were intermingled with dendritic branches of surrounding calbindin D28k-IR cells. Furthermore, we recognized the compartmental organization of glomeruli and two types of periglomerular cells in the MOBs of all of the mammals we examined. These structural features are therefore considered to be common and important organizational principles of the MOBs. J. Comp. Neurol. 472:1,12, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||