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At least 19 recordsLinked to original sources
PubMed2003

[Morphology of olfactory bulb, olfactory tract blood supply affected by anthrosclersis and its clinical significance].

OBJECTIVE: In order to provide morphological evidences for olfactory defect cased by olfactory bulb, olfactory tract ischemia, the origins, numbers, distributions and pathological changes about olfactory bulb, olfactory tract arteries were studied. METHOD: The distributions and pathological changes of olfactory bulb, olfactory tract arteries in 80 sides of adult brain specimens were observed with operation microscope, among which the nourishing arteries and nerve of olfactory tract in two sides aged from 60 to 70 were observed pathohistologically. RESULT: The blood supply of olfactory bulb, olfactory tract comes mainly form artery cerebral and posterior communicainy. 10% of these 60 sides arteries were of multi-branch. 86.3% of them had atheroselerosis. 25.0% of the olfactory bulb and olfactory tract artery were blocked or narrow, and pathological changes in olfactory nerve such as atrophy were observed. CONCLUSION: Excluding other diseases, the olfactory defect in different degree of patients over 60 years old were caused possibly by atheroselerosis of the arteries at base of the brain.

Adult↗
PubMed1982

High specific binding of [3H]GABA and [3H]muscimol to membranes from dendrodendritic synaptosomes of the rat olfactory bulb.

Olfactory bulbs contain dendrodendritic synapses, which occur between granule cells and mitral cells, and gamma-aminobutyric acid (GABA) is thought to act as an inhibitory neurotransmitter at these synapses. Synaptosomes derived from the dendrodendritic synapses of the olfactory bulb were shown previously to contain considerable L-glutamate decarboxylase activity. The subcellular distribution and binding parameters of [3H]GABA and [3H]muscimol binding sites have now been determined in the rat olfactory bulb. Of all fractions examined, crude synaptic membranes (CSM) prepared from the dendrodendritic synaptosomes were shown to have the highest specific binding activity and accounted for nearly all of the total binding activity for both ligands. The specific binding activities for [3H]GABA and for [3H]muscimol were greatly increased after treating the CSM with 0.05% Triton X-100. Binding was shown to be Na+-independent, reversible, pharmacologically specific, and saturable. High- and low-affinity sites were detected for both ligands, and both classes of sites had appreciably lower KD values for muscimol (KD1 = 3.1 nM, KD2 = 25.1 nM) than for GABA (KD1 = 8.6 nM; KD2 = 63.7 nM). The amounts of the high-affinity binding sites for muscimol and GABA were similar (Bmax = 1.7 and 1.5 pmol/mg protein, respectively). The results of the present experiments indicate that the GABA and muscimol binding sites represent the GABA postsynaptic receptor, presumably on mitral cell dendrites, and provide further support for the hypothesis that GABA functions as a neurotransmitter at the dendrodendritic synapses in the olfactory bulb.

Animals↗
PubMed2005

Odor response properties of neighboring mitral/tufted cells in the rat olfactory bulb.

Olfactory perception initiates in the nasal epithelium wherefrom olfactory receptor neurons--expressing the same receptor protein--project and converge in two different glomeruli within each olfactory bulb. Recent evidence suggests that glomeruli are isolated functional units, arranged in a chemotopic manner in the olfactory bulb. Exposure to odorants leads to the activation of specific populations of glomeruli. In rodents, about 25-50 mitral/tufted cells project their primary dendrites to a single glomerulus receiving similar sensory input. Yet, little is known about the properties of neighboring mitral/tufted cells connected to one or a few neighboring glomeruli. We used tetrodes to simultaneously record multiple single-unit activity in the mitral cell layer of anesthetized, freely breathing rats while exposed to mixtures of chemically related compounds. First, we characterized the odorant-induced modifications in firing rate of neighboring mitral/tufted cells and found that they do not share odorant response profiles. Individual units showed a long silent (11.01 ms) period with no oscillatory activity. Cross-correlation analysis between neighboring mitral/tufted cells revealed negligible synchronous activity among them. Finally, we show that respiratory-related temporal patterns are dissimilar among neighboring mitral/tufted cells and also that odorant stimulation results in an individual modification that is not necessarily shared by neighboring mitral/tufted cells. These results show that neighboring mitral/tufted cells frequently exhibit dissimilar response properties, which are not consistent with a precise chemotopic map at the mitral/tufted cell layer in the olfactory bulb.

Action Potentials↗
PubMed1978

Catecholamine innervation of the basal forebrain. III. Olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex.

The catecholamine innervation of the olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex was studied in the rat using biochemical analysis and fluorescence histochemistry. Biochemical studies demonstrate a moderate norepinephrine (NE) content in all olfactory structures, a high dopamine (DA) content in the olfactory tubercle and a low DA content in the olfactory bulb, anterior olfactory nucleus and piriform cortex. Following locus coeruleus lesions NE content decreases 71% in the olfactory bulb, 82% in the anterior olfactory nucleus, 62% in olfactory tubercle and 77% in piriform cortex...

Amygdala↗
PubMed2001

Variability of position of the P2 glomerulus within a map of the mouse olfactory bulb.

Olfactory receptor neurons (ORNs) that express a common odorant receptor molecule target specific glomeruli in the olfactory bulb. We systematically assessed the location of the olfactory glomeruli that receive input from ORNs expressing P2 receptors in the P2-internal ribosome entry site-tau-lacZ mouse. We present a new mapping method that includes an Internet-accessible computer program for generating two- and three-dimensional maps of the glomerular sheet in the olfactory bulbs of mice. Cylindrical coordinates were used to define glomerular location: The coordinates were given as the anteroposterior (AP) distance parallel to the long axis of the bulb (rostrocaudal; RC) and angular measurements with origin defined by the remnant ependymal layer in the center of the granule cell layer in the bulb. Using this method, we can apply rigorous statistical methods to give objective estimates of position and variability. At the 95% confidence interval, the lateral P2 glomerulus lies at coordinates 1,008 microm +/- 306 microm AP x 146 degrees +/- 12 degrees, and the medial P2 glomerulus lies at 1,828 microm +/- 196 microm AP x 204 degrees +/- 8 degrees. We estimate that these coordinates encompass a domain containing 29 and 37 of the 1,800 glomeruli ( approximately 2%) for the lateral and medial glomeruli, respectively. Furthermore, the data reported here demonstrate that the rostrocaudal position of small P2 glomeruli is three times more variable than that of large glomeruli.

Animals↗
PubMed1987

Abrupt decrease in synaptic inhibition in the postnatal rat olfactory bulb.

Olfactory bulb responses to paired-pulse stimulation of the lateral olfactory tract were examined in urethane-anesthetized rats, aged 5 days to adult. Brief inter-pulse intervals resulted in a depression of test responses at all ages. The magnitude of this depression decreased dramatically between postnatal days 19 and 20 to approach adult levels. Longer inter-pulse intervals resulted in a facilitation of test response amplitude in adult animals. This facilitation was evident at adult levels by postnatal day 10. These results suggest that both inhibitory and facilitatory synaptic mechanisms appear early in the course of rat olfactory bulb development. Furthermore, presumed granule cell-mediated inhibition is present at unusually high levels in the developing bulb, decreasing sharply between days 19 and 20.

Aging↗
PubMed1994

Ultrastructure of lamellar granules coating glial cell basal lamina in the olfactory bulb and olfactory subtracts of goldfish.

Lamellar granules, 35 to 80 nm in diameter, are observed in the pia-arachnoid tissue of regenerated olfactory bulb and olfactory subtracts of the goldfish. The granules correspond to multiple stacks of disks which cover basal lamina of both pial and ependymal cell layers and blood vessels. The granules are also in close association with collagen fibril bundles. The granules are observed only in young goldfish or after bilateral olfactory tract transection in 1 year postoperated animals. Our findings suggest that these granules are secreted by connective tissue cells in response to damage associated with bilateral olfactory tract transection. Coexisting extracellular free granules and the granules covering basal lamina are simultaneously found in regenerated olfactory bulb and olfactory tract. Many of our findings, as far as we know, have not been described previously. The composition and function of these granules are at present unknown.

Aging↗
PubMed1990

Morphology of neuropeptide Y-immunoreactive neurons in the cat olfactory bulb and olfactory peduncle: postnatal development and species comparison.

The distribution and morphology of Neuropeptide Y-immunoreactive (NPY-ir) neurons in the olfactory bulb and the olfactory peduncle was studied in the adult cat and rat, and the common marmoset Callithrix jacchus. Significant species differences were not observed. In all three species, the population of NPY-ir neurons is localized in the white matter extending from the main olfactory bulb to the border of the striatum. The neurons are characterized by a conspicuously looping axonal ramification pattern with some major collaterals running toward the olfactory bulb and others running toward the internal olfactory tract. The former, ipsilateral projection terminates in the granule cell layer of the main and accessory olfactory bulb and in layer II/III of the anterior olfactory nucleus. Reconstruction of the latter projection has revealed that the fibers are continuous with the olfactory limb of the anterior commissure and the anterior commissure proper suggesting a commissural contralateral projection. The analysis of the postnatal development of the cat NPY neuron system supports this assumption in a very clear-cut way. In young animals growing fibers are observed to cross the brachium of the commissure. The NPY neuron system develops postnatally. The maximum cell number is reached during the third postnatal week. The appearance of more and more NPY-ir neurons slightly precedes the formation of the terminal fields and of the fiber projection in the internal olfactory tract. The density of this early fiber projection by far exceeds the fiber density observed in the adult. Later in development the fiber density in the olfactory limb and the anterior commissure becomes considerably reduced. In contrast, the plexus density in the anterior olfactory nucleus and the granule cell layer of the main and accessory olfactory bulb undergoes only a slight reduction, and the NPY-ir cell number remains roughly constant. These observations suggest that the ipsilateral NPY-ir projection remains largely unchanged, in contrast to the contralateral projection, which exists to a large extent only for the first four postnatal months. The observation that the NPY neuron system gives rise to a contralateral projection does not support a classification of NPY neurons as short axon cells.

Animals↗
PubMed1996

Investigation of the role of interneurons and their modulation by centrifugal fibers in a neural model of the olfactory bulb.

Olfactory bulb processing results from the interaction of relay neurons with two main categories of interneurons which mediate inhibition in two distinct layers: periglomerular cells and granule cells. We present here a neural model of the mammalian olfactory bulb which allows to separately investigate the functional consequences of the two types of interneurons onto the relay neurons responsiveness to odors. The model, although built with simplified representations of neural elements generates various aspects of neural dynamics from the cellular to the populational level. We propose that the combined action of centrifugal control at two different layers of processing is complementary: reduction of the number of active relay neurons responding to a given odorant through increased activity of periglomerular cells, and an increase of response intensity of active mitral cells through decrease of granule cell inhibition.

Animals↗
PubMed1979

Mechanisms of augmented field potential responses in the rat olfactory bulb.

Olfactory bulb field potential and single unit responses to paired pulse stimulation of the lateral olfactory tract were observed in the rat. In agreement with previous reports, surgical levels of barbiturate anesthesia prolonged the period of diminution of the field potential responses to the test pulse relative to the effect seen under light anesthesia. Very deep barbiturate anesthesia (sufficient to depress the EEG) led to decreased responses to the primary pulse but augmented responses to the test pulse. Urethane and ether anesthesia produced augmented test responses without severely depressing the EEG and without producing a period of diminished test responses. Single unit recordings failed to show external plexiform layer units excited at the time of maximal augmentation of the field potential. Simultaneous single unit and field potential recordings showed that prolonged diminution of the field potential response was associated with prolonged suppression of unit responses to the test pulse, while augmented field potential responses were associated with decreased suppression of unit responses to the test pulse. These observations are most easily explained by the assumption of temporal facilitation in the synaptic output of mitral and tufted cells. This facilitation is masked by feedback inhibition under some conditions, particularly under barbiturate anesthesia.

Anesthesia, General↗
PubMed2000

Local permutations in the glomerular array of the mouse olfactory bulb.

Olfactory sensory neurons expressing a given odorant receptor gene project their axons with great precision to a few specific glomeruli in the olfactory bulb. It is not clear to which extent the positions of these glomeruli are fixed. We sought to evaluate the constancy of the glomerular array in the mouse by determining the relative positions of glomeruli for various odorant receptors, using a method that affords single-axon resolution, and in a large number of bulbs. We used a genetic strategy to visualize neuronal populations that express one of three members of the mOR37 subfamily. We generated by gene targeting five strains of mice in which expression of a given mOR37 gene is linked to expression of an axonal maker, which is either taulacZ or tauGFP. The patterns of marker expression faithfully mimic those of the cognate receptors. Axons of neurons expressing a given mOR37 gene converge onto one or two glomeruli per bulb. Each mOR37 gene has its own glomeruli, and the mOR37 glomeruli are grouped within a restricted domain of the bulb. Serial sectioning of 214 bulbs reveals that the relative positions of the three types of glomeruli are not fixed but display local permutations. Importantly, this is also the case among the two bulbs from one individual, ruling out the genetic manipulation itself and differences in genetic background or olfactory experience as causes for the observed variability. These local permutations may reflect the developmental history of the glomeruli and are relevant for the construction of spatial odor maps.

Alleles↗
PubMed1976

The efferent connections of the olfactory bulb and accessory olfactory bulb in the snakes, Thamnophis sirtalis and Thamnophis radix.

The efferent connections of the olfactory bulb and accessory olfactory bulb of two species of garter snakes, Thamnophis sirtalis and T. radix were studied with experimental anterograde degeneration techniques. Axons of cells located in the olfactory bulb terminate ipsilaterally in all parts of the anterior olfactory nucleus, olfactory tubercle and lateral pallium. In addition, some axons enter the ipsilateral stria medullaris thalami, cross the midline in the habenular commissure, enter the contralateral stria medullaris thalami and terminate in the contralateral lateral pallium. The axons of cells in the accessory olfactory bulb course through the telencephalon completely separated from the fibers of olfactory bulb origin and terminate predominantly in the nucleus sphericus. These results confirm previous reports of the separation between the central projections of the olfactory and vomeronasal systems in a variety of vertebrates. The totality of the separation between these two systems coupled with the extensive development of the vomeronasal-accessory bulb system in these snakes suggests that they may be ideal subjects for further research on the functional significance of the vomeronasal system.

Animals↗
PubMed2006

Role of centrifugal projections to the olfactory bulb in olfactory processing.

While there is evidence that feedback projections from cortical and neuromodulatory structures to the olfactory bulb are crucial for maintaining the oscillatory dynamics of olfactory bulb processing, it is not clear how changes in dynamics are related to odor perception. Using electrical lesions of the olfactory peduncle, sparing output from the olfactory bulb while decreasing feedback inputs to the olfactory bulb, we demonstrate here a role for feedback inputs to the olfactory bulb in the formation of odor-reward associations, but not for maintaining primary bulbar odor representations, as reflected by spontaneous odor discrimination.

Animals↗
PubMed2004

Interplay between local GABAergic interneurons and relay neurons generates gamma oscillations in the rat olfactory bulb.

Olfactory stimuli have been known for a long time to elicit oscillations in olfactory brain areas. In the olfactory bulb (OB), odors trigger synchronous oscillatory activity that is believed to arise from the coherent and rhythmic discharges of large numbers of neurons. These oscillations are known to take part in encoding of sensory information before their transfer to higher subcortical and cortical areas. To characterize the cellular mechanisms underlying gamma (30-80 Hz) local field potential (LFP) oscillations, we simultaneously recorded multiunit discharges, intracellular responses, and LFP in rat OB slices. We showed that a single and brief electrical stimulation of olfactory nerve elicited LFP oscillations in the mitral cell body layer lasting >1 sec. Both action potentials and subthreshold oscillations of mitral/tufted cells, the bulbar output neurons, were precisely synchronized with LFP oscillations. This synchronization arises from the interaction between output neurons and granule cells, the main population of local circuit inhibitory interneurons, through dendrodendritic synapses. Interestingly enough, the synchronization exerted by reciprocal synaptic interactions did not require action potentials initiated in granule cell somata. Finally, local application of a GABA(A) receptor antagonist at the mitral cell and external plexiform layers confirmed the exclusive role of the granule cell reciprocal synapses in generating the evoked oscillations. We concluded that interneurons located in the granule cell layer generate synaptic activity capable of synchronizing activity of output neurons by interacting with both their subthreshold and spiking activity.

Action Potentials↗
PubMed2003

Subzonal organization of olfactory sensory neurons projecting to distinct glomeruli within the mouse olfactory bulb.

Olfactory sensory neurons located in the nasal neuroepithelium send their axons directly into the olfactory bulb, where they contact the dendrites of second-order neurons in specialized spherical structures called glomeruli; each sensory neuron projects to a single glomerulus. All neurons expressing the same odorant receptor gene are confined to distinct zones within the epithelium and converge their axons onto a small number of common glomeruli. In the present study, we analyzed transgenic mouse lines in which the projection of a neuron population expressing a particular receptor gene can be visualized as a result of axonal markers that are coexpressed. The target glomeruli could thus reproducibly be identified and allowed to deposit retrograde tracers precisely. After an appropriate incubation time, olfactory sensory neurons within distinct areas of the olfactory epithelium were labeled. The two subpopulations of neurons retrogradely stained by differently colored fluorescent dyes deposited at the dorsal and the dorsomedial glomerulus, respectively, were found to be segregated within distinct areas of the expression zone, where the cells expressing the same receptor type displayed a stochastic distribution.

Animals↗
PubMed1997

Long-term recording of olfactory and vomeronasal stimulant-induced waves from the turtle main olfactory bulb and accessory olfactory bulb.

Recording of stimulant-induced waves (bulbar responses) from the main olfactory bulb is a useful tool for measuring quantitative stable olfactory responses. There is a good relationship between the olfactory bulbar response, olfactory nerve response and electroolfactogram (EOG), suggesting that the bulbar response reflects events in receptor cells. The modern whole-cell recording technique offers direct information on olfactory transduction in single cells, but it requires long experimental periods and many animals. On the other hand, analysis of bulbar responses provides useful information and requires the use of few animals. For example, we found that cAMP-increasing and IP3-increasing odorants were not distinctly received by the turtle olfactory organ by measuring olfactory bulbar responses and analyzed with a multidimensional scaling from about 60 animals. However, to record similar odor responses from isolated turtle olfactory neurons, at least 200 animals would be necessary. Bulbar responses are recorded with electrodes implanted into or located on the main olfactory bulb. When electrodes are located on the olfactory bulb surface, it is possible to record stable responses over a period of 3 days. These methods were applied successfully to the accessory olfactory bulb. In this paper, we describe the protocols used for recording of the stimulant-induced waves from the main and accessory olfactory bulb.

Adaptation, Physiological↗
PubMed1999

Tyrosine hydroxylase immunoreactive structures in the aged human olfactory bulb and olfactory peduncle.

We studied the anatomical distribution of dopaminergic structures in the normal, aged, human olfactory bulb and olfactory peduncle with a monoclonal antibody against tyrosine hydroxylase. Three different tyrosine hydroxylase containing cell groups are present in the olfactory bulbs: (1) a group of round, medium-sized cells within and around the glomeruli; (2) cells in the external plexiform layer; and (3) cells that are scattered in the stratum album. Occasionally, a few labeled neurons can be observed in the granule cell layer. In the olfactory peduncle a few labeled cells are present in the superficial layers just underneath the pia. Tyrosine hydroxylase containing terminal-like structures are present in the glomerular layer and the external plexiform layer. In a few cases dense terminal labeling is also observed in the cell groups that constitute the anterior olfactory nucleus. In the olfactory peduncle scattered labeled fibers are present. In addition, the present study makes clear that quantitative differences exist between the individual cases for which no explanation could be found.

Aged↗