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At least 19 recordsLinked to original sources
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↗
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↗
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↗
PubMed1975

The differential projections of the olfactory bulb and accessory olfactory bulb in mammals.

Three species were studied, the rabbit, opossum and rat. Lesions of the main olfactory bulb caused terminal degeneration, assayed by the Fink-Heimer method, to occur in the ipsilateral olfactory tubercle, prepyriform cortex (including its periamygdaloid part), ventrolateral entorhinal area, and in anterior and posterolateral divisions of the cortical amygdaloid nucleus. The various parts of the ipsilateral anterior olfactory nucleus and the rostroventral end of the anterior continuation of the hippocampus (hippocampal rudiment) also received this projection. Lesions of the accessory olfactory bulb, which receives its sensory input from the vomeronasal (Jacobson's) organ, caused terminal degeneration to occur in the medial amygdaloid nucleus and in a posteromedial part of the cortical amygdaloid nucleus. This projection was conveyed by an accessory olfactory tract, which is accompanied in part of its course by a small nucleus, the bed nucleus of the accessory olfactory tract. The accessory olfactory tract is initially a part of the lateral olfactory tract but becomes increasingly indivuated at more posterior levels. It parts company with the lateral olfactory tract at the rostral end of the amygdaloid region, and, in addition to distributing to the medio-cortical amygdaloid region, it enters the stria terminalis to terminate in the bed nucleus of the stria terminalis in a small region bearing cytoarchitectonic resemblance to the medial amygdaloid nucleus. The topographic segregation of the areas of termination of the olfactory and accessory olfactory (vomeronasal) projections is suggestive of a functional dichotomy in the organization of the olfactory system...

Amygdala↗
PubMed1991

Distribution and morphology of substance P-immunoreactive structures in the olfactory bulb and olfactory peduncle of the common marmoset (Callithrix jacchus), a primate species.

The present study describes the morphology and distribution of substance P-immunoreactive (SP-ir) elements in the olfactory bulb (OB) and olfactory peduncle (OP) of the common marmoset (Callithrix jacchus), a primate species. SP-ir neurons are very abundant in the OB and belong to two types. External tufted cells are present in the glomerular layer (GL), whereas granule cells are found in the deeper layers, especially in the granule cell layer (GRL), but also scattered in the OP. SP-ir fibers, putatively of central origin, were identified in the OP. They ascend into the bulbar layers. The SP-chemoarchitecture of the marmoset OB and OP does not differ more from rat, guinea pig and cat, than the SP-chemoarchitecture of these species varies among one another.

Animals↗
PubMed1992

Kindling and electrode effects on the benzodiazepine receptors density of olfactory bulb and hippocampus after olfactory bulb kindling.

The olfactory bulb (OB) kindling is a model of limbic secondary generalized epilepsy. Ten days after the completion of OB kindling, we have studied the long term effects of both electrode insertion and kindling on the binding of [3H]diazepam to crude mitochondrial fractions. On the one hand, we have shown that electrode implantation in sham-operated controls induced an obvious increase in benzodiazepine (BZD) receptor density (Bmax) only at the site of the electrode in comparison to sham-unoperated rats. These results might indicate an additional mechanism extending earlier observations reported by others, who have shown that prolonged electrode implantation induced changes in sham-operated and kindled rats. On the other hand, the long lasting effect of OB kindling on the binding parameters of [3H]diazepam was examined in the focus and in the hippocampus. The results indicate a bilateral increase of BZD receptors in the OB and an ipsilateral increase in the hippocampus. These changes might be a regulation phenomenon in response to a hyperexcitability state and to focal stimulations.

Animals↗
PubMed1992

Olfactory bulb transplantation into the olfactory bulb of neonatal rats: a WGA-HRP study.

After unilateral bulbectomy in neonatal (P1-P5) rats, autoradiographically prelabeled presumptive olfactory bulbs from E15 and E17 embryos were transplanted in place of the removed tissue. After 2-7 months, the animals received injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the piriform cortex. Nine of the twenty animals revealed WGA-HRP-positive neurons among neurons autoradiographically labeled, providing thus evidence that the axons of the output neurons from the homotopically transplanted olfactory bulb reconnect with the host piriform cortex.

Animals↗
PubMed1991

Olfactory bulb transplantation into the olfactory bulb of neonatal rats: an autoradiographic study.

Tritiated thymidine prelabeled presumptive olfactory bulbs (E15-E17, and E19) were homotopically transplanted in unilaterally partially or totally bulbectomized neonatal rats (P1-P5). [3H]thymidine was injected to pregnant rats at the time when the large neurons of the bulb were undergoing cellular division. After postoperative survival times from 20 days to 7 months, the animals were sacrificed and processed for histological, immunohistochemical and autoradiographic observations. The nuclear autoradiographic label allowed easy recognition of the transplanted tissue in totally bulbectomized animals after short survival and in partially bulbectomized animals after long survival. The autoradiographic label was strictly confined to the transplanted tissue and intermingling of host and donor neurons was never observed. The reliability of the autoradiographic technique in our study will enable us to mark those neurons whose axons can be demonstrated, by retrograde tracing methods, to establish connections with the host brain.

Animals↗
PubMed1992

Localization of corticotropin-releasing factor-like immunoreactivity in monkey olfactory bulb and secondary olfactory areas.

Electrophysiological and anatomical observations suggest that terminals of olfactory bulb mitral cells ending in rat primary olfactory cortex exert certain postsynaptic effects via an excitatory amino acid neurotransmitter. Recent anatomical studies have shown that several peptides, most notably corticotropin-releasing factor (CRF) (Imaki et al., '89) Brain Res., 496: 35-44), are also localized within rat olfactory bulb projection neurons, thus raising the possibility that there is a peptide cotransmitter in this system. In contrast to the availability of data for rodents, very little is known about the distribution of peptides and other putative transmitters in the olfactory systems of primate species. In the present study, sections through the olfactory bulb and its target areas were obtained from two monkey species (Saimiri sciureus and Macaca fascicularis) and processed for immunohistochemistry with a well-characterized polyclonal antiserum directed against the human form of CRF. Virtually identical results were obtained in the two species. Within the olfactory bulb, nearly all mitral and many tufted cells contained CRF-like immunoreactivity. CRF-positive fibers were seen within the olfactory tract and olfactory stria, which contain the axons of mitral and tufted cells. Within the anterior olfactory nucleus and layer Ia of the olfactory tubercle and piriform cortex, immunoreactivity was seen within fine processes, as well as in coarse, varicose fibers and isolated puncta. CRF-positive cells were seen within layer III of the olfactory tubercle and piriform cortex. Immunoreactive fibers and varicosities were also seen within olfactory-recipient regions of the amygdala and entorhinal cortex. These observations suggest that CRF may act as a transmitter and/or neuromodulator in primate olfactory system.

Amygdala↗
PubMed1991

Calbindin-D-28k-like immunoreactive structures in the olfactory bulb and anterior olfactory nucleus of the human adult: distribution and cell typology--partial complementarity with parvalbumin.

Calbindin-D-28k and parvalbumin are calcium-binding proteins. The laminar distribution and morphological features of calbindin-D-28k-like immunoreactive structures were studied in 60-microns-thick sections of the human olfactory bulb. Except for the olfactory nerve layer, immunoreactive neurons were present in all layers of the olfactory bulb. They reached highest densities in the external plexiform layer and internal granule cell layer. Considerable numbers of calbindin-like nerve cells were also found in the olfactory tract and in distal portions of the anterior olfactory nucleus. When comparing the distribution of calbindin-positive structures to that of parvalbumin-positive ones a partially complementary distribution pattern was found. Calbindin-like immunoreactive portions of the anterior olfactory nucleus and olfactory tract were mirrored by immunonegative areas in adjacent sections stained for parvalbumin. Using the combined pigment-Nissl procedure we observed the presence of lipofuscin deposits in nearly 80% of all the calbindin-immunoreactive neurons analysed. Moreover, analysis of their lipofuscin deposits rendered the further differentiation of morphologically similar neuronal subpopulations possible. In contrast, all parvalbumin-like immunoreactive neurons remained free of lipofuscin granules.

Adult↗
PubMed1990

Excitatory synaptic transmission in cultures of rat olfactory bulb.

1. Olfactory bulb neurons were dissociated from neonatal rats and plated at low density on a confluent layer of olfactory bulb astrocytes. Intracellular stimulation of presumptive mitral/tufted (M/T) cells evoked monosynaptic excitatory postsynaptic potentials (EPSPs) in adjacent neurons. Whole-cell recording techniques and a flow-pipe drug delivery system were used to compare EPSPs with voltage-clamp recordings of currents evoked by excitatory amino acids (EAA) including N-acetylaspartylglutamate (NAAG), a putative mitral cell transmitter. 2. Cultured olfactory bulb neurons were morphologically and physiologically distinct. Large pyramidal-shaped neurons were present, which were NAAG immunoreactive; stimulation of these neurons invariably evoked EPSPs, suggesting that they were M/T cells. The majority of small bipolar neurons were glutamic acid decarboxylase (GAD) immunoreactive consistent with granule or periglomerular gamma-aminobutyric acid (GABA)ergic interneurons. 3. Monosynaptic EPSPs between M/T cells could be separated into fast and slow components by the use of EAA receptor antagonists. A fast component with a time-to-peak of 7.7 +/- 1.0 (SE) ms and half-width of 31.8 +/- 7.4 ms was blocked by the non-NMDA receptor antagonist 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX, 2.5 microM). The slow component (time-to-peak = 41.4 +/- 7.2 ms; half-width = 218.9 +/- 40.4 ms) was blocked by the N-methyl-D-aspartate (NMDA) receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP5, 100 microM). 4. Under voltage clamp, flow-pipe applications of NAAG (10-1,000 microM) evoked inward currents at a holding potential of -60 mV in Mg-free solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1991

Olfactory deprivation increases dopamine D2 receptor density in the rat olfactory bulb.

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.

Aging↗
PubMed1978

Forebrain projections of the pigeon olfactory bulb.

The olfactory system of the pigeon (Columba livia) was examined. Our electrophysiological and experimental neuroanatomical (Fink-Heimer technique) data showed that axons from the olfactory bulb terminated in both sides of the forebrain. The cortex prepiriformis (olfactory cortex), the hyperstriatum ventrale and the lobus parolfactorius comprised the uncrossed terminal field. The crossed field included the paleostriatum primitivum and the caudal portion of the lobus parolfactorius, areas which were reached through the anterior commissure. In this report the relationships between areas that receive olfactory information and the possible roles that olfaction plays in the birds' behavior are discussed.

Animals↗
PubMed1992

Neural circuit computation: complex patterns in the olfactory bulb.

The olfactory bulb principal neurons show complex responses during olfactory stimulation that are characterized by periods of profound suppression, temporal patterns of activity, and nonmonotonic intensity response functions. The model presented here suggests that these features may arise from changing spatial patterns of activity across the bulbar surface due to restricted (chemotopic) activation in bulbar glomeruli. The model is based on a simplified version of the bulbar neural circuit as it is presently known from anatomical and physiological investigations and provides explanations for several anomalous bulbar response patterns.

Axons↗