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PubMed1994

Gonadotropin releasing hormone (GnRH) neurons project to growth hormone and somatolactin cells in the steelhead trout.

Analysis of gene expression using gonadotropin-releasing hormone (GnRH) antisense oligonucleotide confirmed by immunocytochemical localization the occurrence of GnRH neurons along the nervus terminalis in the steelhead trout (Oncorhynchus mykiss). Double-label immunocytochemistry revealed the distribution of mammalian (m), salmon (s) and chicken II (cII)-type GnRHs and various pituitary hormones. Both sGnRH and mGnRH appeared to be colocalized in the same cells of the nervus terminalis. Chicken GnRH II-immunoreactivity was found only in fibers and terminals. In the younger fish [73 and 186 days after fertilization (DAF)] GnRH neurons were seen rostral to the olfactory bulb. A novel GnRH ganglion, along the nervus terminalis, was found at the cribiform bone (gCB). A few non-immunoreactive rounded cells were seen among the GnRH neurons. A second smaller ganglion was seen at the most rostrally located part of the ventromedial olfactory bulb (gROB). In the older fish (850 DAF) GnRH neurons were also observed in the basal forebrain. A small group of neurons (2-3 cells), at the caudoventromedial border of the olfactory bulb, formed the ganglion terminale. Occasionally isolated GnRH-immunoreactive cells were seen at the base of the olfactory epithelium, along the ventromedial margins of the olfactory nerve. GnRH-immunoreactive and GnRH mRNA expressing neurons were absent from midbrain regions at the ages observed. GnRH-immunoreactive fibers were present only in older fish. The pattern of distribution of fibers that were immunoreactive to all three forms of GnRH was identical. Fibers were seen along the medial side of the olfactory nerve, throughout the brain and in the pituitary, associated with growth hormone and somatolactin cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Cell migration from the transplanted olfactory placode in Xenopus.

The eye vesicle of Xenopus borealis has been replaced with the transplanted olfactory primordium from Xenopus laevis in an attempt to determine whether cells from the transplant could migrate along the regrowing olfactory nerve and become incorporated into the CNS of the host. The use of X. laevis and X. borealis pairs allowed us to distinguish the cells of the host from those of the donor at the cellular level by means of the characteristic fluorescent nuclear spots (Q bands) of X. borealis. Transplantation was performed on pairs of animals at stages 23/24. The olfactory anlage was readily incorporated into the host, often fusing with the host homolateral organ and inhibiting the regrowth of the eye vesicle. An olfactory nerve developed from the transplanted organ. In the majority of cases, the nerve reached the diencephalon at the level of entrance of the optic nerve. Along the nerve originating from the transplanted organ we observed a stream of cells with the characteristics of the donor. These cells penetrated the host's CNS and became incorporated into it. The nature of these cells has not been ascertained by specific neuronal markers. However, on the basis of their morphology and disposition, the hypothesis suggested is that some of the migrating cells are neurons.

Animals↗
PubMed2006

Chronically injured corticospinal axons do not cross large spinal lesion gaps after a multifactorial transplantation strategy using olfactory ensheathing cell/olfactory nerve fibroblast-biomatrix bridges.

Transplantation of mixed cultures containing olfactory ensheathing cell (OEC) and olfactory nerve fibroblasts (ONF) has been shown to stimulate regrowth of both acutely and chronically injured corticospinal (CS) axons across small spinal cord lesion gaps. Here, we used a multifactorial transplantation strategy to stimulate regrowth of chronically injured CS axons across large spinal cord lesion gaps. This strategy combined the transplantation of aligned OEC/ONF-biomatrix complexes, as described previously (Deumens et al. [2004] Neuroscience 125:591-604), within the lesion gap with additional OEC/ONF injections rostral and caudal to the lesion site. We show an enhanced presence of injured CS axons directly rostral to the lesion gap, with no effects on injured CS axons at or caudal to the lesion gap. Furthermore, injured CS axons did not penetrate the OEC/ONF-biomatrix complex within the lesion gap. The enhanced presence of CS axons rostral to the lesion gap was not accompanied by any recovery of behavioral parameters assessed with the BBB locomotor rating scale or CatWalk gait analysis. We conclude that our multifactorial transplantation strategy should be optimized to create an OEC/ONF continuum in the injured spinal cord and thereby stimulate regrowth of injured CS axons across large spinal lesion gaps.

Animals↗
PubMed1978

[Nature of the impulse activity in the anterior portions of the fish olfactory bulb].

The impulse activity of anterior portions of the fish olfactory bulb depends on coming of signals from the receptors as shown by the fact that action of novokain on the receptors entirely suppressed the activity. A direct application of CoCl2 solution (1--1.5 mM) had no effect on either spontaneous or evoked by adequate stimulation impulse activity in these areas which indicates its presynaptic, i.e. the receptor nature. The surface structures of the bulb anterior portions did not respond to electric stimulation of the olfactory tract while the electric stimulation of these structures evoked a response in the olfactory nerve which corresponds to the conclusion of the receptor nature of the impulse activity in fibers on the surface of the bulb anterior portions.

Animals↗
PubMed1990

The development of a simple scaffold of axon tracts in the brain of the embryonic zebrafish, Brachydanio rerio.

We have examined neuronal differentiation and the formation of axon tracts in the embryonic forebrain and midbrain of the zebrafish, between 1 and 2 days postfertilisation. Axons were visualised with three techniques; immunocytochemistry (using HNK-1 and antiacetylated tubulin antibodies) and horseradish peroxidase (HRP) labelling in whole-mounted brains, and transmission electron microscopy. Differentiation was monitored by histochemical staining for acetylcholinesterase (AChE). These independent methods demonstrated that a simple grid of tracts and commissures forms the initial axon scaffold of the brain. At 1 day, the olfactory nerve, four commissures, their associated tracts and three other non-commissural tracts are present. By 2 days, these tracts and commissures have all greatly enlarged and, in addition, the optic nerve and tract, and three new commissures and their associated tracts have been added. Small applications of HRP at various sites revealed the origins and projections of some of these earliest axons. Retrogradely labelled cell bodies originated from regions that were also positive for AChE activity. At 1 day, HRP-labelled axons were traced: (1) from the olfactory placode through the olfactory nerve to the dorsal telencephalon; (2) from the telencephalon into the tract of the anterior commissure and also to the postoptic region of the diencephalon; (3) from the hindbrain through the ventral midbrain and diencephalon to the postoptic commissure; (4) from the dorsal diencephalon (in or near the epiphysis) to the tract of the postoptic commissure; (5) from ventral and rostral midbrain through the posterior commissure. Three new projections were demonstrated at 2 days: (1) from the retina through the tract of the postoptic commissure to the tectum; (2) from the telencephalon to the contralateral diencephalon; and (3) from the telencephalon to the ventral flexure. These results show that at 1 day, the zebrafish brain is impressively simple, with a few small, well-separated tracts but by 2 days the brain is already considerably more complex. Most of the additional axons added onto pre-existent tracts rather than pioneered new ones supporting the notion that other axons play a crucial role in the guidance of early central nervous system (CNS) axons.

Acetylcholinesterase↗
PubMed1996

Organization of GnRH and FMRF-amide systems in two primitive bony fishes (order polypteriformes).

To investigate the evolution of the neural organization of gonadotropin-releasing hormone (GnRH), we have examined GnRH-immunoreactivity in two brachiopterygian fishes (Polypterus palmas and Calamoichthys calabaricus). Distal regions of the terminal nerve (TN) within the medial olfactory nerve contained clusters of GnRH-immunoreactive (ir) perikarya (< 10 microns). More proximal, isolated GnRH-ir neurons were present among TN fascicles as they penetrated the ventral forebrain, and a few ir neurons were observed accompanying GnRH-ir fibers in the rostromedial telencephalon. GnRH-ir neurons were not observed in the preoptic area or ventral hypothalamus. In contrast, a small group of GnRH-ir neurons was localized in the periventricular nucleus of the posterior tuberculum. GnRH-ir fibers were present in widespread areas of the brain, including the olfactory bulb, telencephalon, optic nerve, hypothalamus, thalamus, habenula, optic tectum, tegmentum, pituitary and spinal cord. To further characterize projections of TN neurons, we utilized antiserum to FMRF-amide, a small peptide produced by TN cells in other vertebrates. Perikarya that were FMRF-amide-ir within the TN were similar in distribution to GnRH-TN neurons, and the distribution of FMRF-amide-ir fibers overlapped those of GnRH-ir fibers, thus providing a useful marker for identifying TN projections. An additional population of FMRF-amide-ir neurons was present in the periventricular hypothalamus. Our results suggest that in the polypteriformes, GnRH and FMRF-amide neurons of the TN are similar to those observed in other vertebrates; however, the paucity of GnRH cells in the basal forebrain may be unique to primitive actinopterygians and elasmobranchs, and may result from the lack of migration of GnRH neurons into the forebrain, a phenomenon that likely occurs in all other vertebrate classes. Finally, the identification of GnRH-ir neurons in the posterior tuberculum is consistent with similar, and perhaps homologous, GnRH neurons present in nearly all other vertebrate classes.

Animals↗
PubMed1994

Distribution of vesicular stomatitis virus proteins in the brains of BALB/c mice following intranasal inoculation: an immunohistochemical analysis.

Earlier studies have shown that intranasal instillation of vesicular stomatitis virus (VSV), a negative-sense RNA virus, in mice and rats can result in infection of the brain, hind-limb paralysis and death. Using an antiserum directed against VSV proteins, we sought to determine the potential neuronal and non-neuronal pathways VSV utilize, for central nervous system dissemination in BALB/c mice. Within 12 h following intranasal inoculation of VSV, VSV antigen could be detected in the olfactory nerve layer of the ipsilateral olfactory bulb. Within 3-4 days post-inoculation (p.i.), VSV had disseminated into the glomeruli of the olfactory bulb as well as the anterior olfactory nuclei that were ipsilateral to the VSV instillation. Within the glomeruli, VSV antigen was more prevalent in the granule cells than in the mitral cells. Correspondingly, the lateral olfactory tract, where axons of mitral cells course, remained VSV negative throughout 7 days p.i. By 7 days p.i., viral proteins were detected in several additional regions extending to the brainstem. These included regions involved in theta-rhythm generation during exploration and REM sleep, i.e. the septal nuclei, the supramammillary body, and the hippocampal formation, as well as the amygdaloid complex and brainstem neuromodulatory centers, such as the dorsal raphé and locus coeruleus. Structures abutting the ventricular surfaces, such as the dorsal cochlear nucleus, were also labeled. Tracts immunoreactive to VSV included the dorsal tegmental tract, fascia retroflexus, Probst tract, and mesencephalic tract of the trigeminal motor nerve. Besides the lateral olfactory tract, tracts that remained VSV negative included the anterior commissure, the corpus callosum and the mammillary peduncle. The pattern of VSV immunoreactivity supports the idea that following infection of the olfactory bulb glomeruli, VSV spreads via both ventricular surfaces and retrograde transport within axons of neuromodulatory transmitter systems innervating the olfactory bulb. Conversely, regions exhibiting low levels of VSV antigen are not likely to be involved in VSV dissemination. In particular, the paucity of VSV antigen in some of the terminal fields of neuromodulatory systems indicate that anterograde transport is more selective than retrograde transport. Surprisingly, the principal neurons of the olfactory glomeruli, thalamus, cerebral cortex and the hippocampus, all of which use L-glutamate as the excitatory neurotransmitter, are much less involved in viral dissemination.

Administration, Intranasal↗
PubMed1999

The extended transbasal approach: a quantitative anatomical and histological study.

Since its introduction in 1972 the transbasal approach to the anterior fossa and sphenoethmoidal region has undergone a number of modifications. The extended transbasal approach with preservation of olfaction not only improves exposure of the anterior fossa, but also provides access to the clivus as far inferiorly as the foramen magnum. An anatomical study has been undertaken to photographically demonstrate and quantify the varying degrees of exposure that this technique provides. The pituitary stalk was used as an intracranial target. The amount of exposure was compared using a standard subfrontal approach, a transbasal approach and an extended transbasal with preservation of olfaction. In addition, a histological study was carried out to investigate the level to which identifiable olfactory nerves extended into the nasal mucosa. The anatomical study demonstrates the area of the "external window of exposure" can be doubled using a transbasal approach and more than quadrupled using the extended transbasal approach, when gaining access to the pituitary stalk. In addition, the study highlights the exposure of other anatomical areas, such as the medial orbit, the cavernous sinus, the clivus and the vertebrobasilar complex. The histological study establishes that the olfactory nerves extend only 10 mms below the cribriform plate.

Brain↗
PubMed1988

Immunocytochemical localization of LH-RH in the brain and pituitary of the catfish, Clarias batrachus (Linn.).

An elaborate organization of luteinizing hormone-releasing hormone (LH-RH) immunoreactive (ir) cells and fibers was encountered in the olfactory system of Clarias batrachus. In addition to the ir structures in the olfactory nerve, peripheral area of the olfactory bulb, and the medial olfactory tract (MOT), ir cells and fibers were prominently seen in the lamellae of the olfactory organ. Perikarya showing varying degrees of intensity of immunoreaction were observed along the base of the forebrain in the nucleus preopticus basalis lateralis, nucleus preopticus periventricularis, nucleus preopticus, nucleus lateralis tuberis pars posterior, and the pituitary. Some cells were also noticed in the midbrain tegmentum. A well-defined system of ir fibers from the MOT penetrated the telencephalon and curved dorsocaudally into the pars supracommissuralis above the anterior commissure (AC); while some fibers decussate in the AC, others extended posteriorly into the diencephalon. A fairly dense network of beaded ir fibers was seen in the basal forebrain, conspicuous around the organum vasculosum laminae terminalis and caudally traceable as far as the neurohypophysis; some immunostained fibers appear to be directly contacting with the cells of the proximal pars distalis. Fibers were also witnessed in the optic chiasma and in the inner plexiform layer of the retina. Solitary fibers were noticed in certain circumscribed telencephalic areas, caudal hypothalamus, posterior commissure, midbrain tegmentum, cerebellum, and ventral medulla oblongata. The highly organized LH-RH containing system in C. batrachus is indicative of its elaborate role in synchronization of the reproductive processes and the environmental cues.

Animals↗
PubMed1990

Distribution of FMRFamide-like immunoreactivity in the brain, retina and nervus terminalis of the sockeye salmon parr, Oncorhynchus nerka.

Neurons displaying FMRFamide(Phe - Met - Arg - Phe - NH2)-like immunoreactivity have recently been implicated in neural plasticity in salmon. We now extend these findings by describing the extent of the FMRF-like immunoreactive (FMRF-IR) system in the brain, retina and olfactory system of sockeye salmon parr using the indirect peroxidase anti-peroxidase technique. FMRF-IR perikarya were found in the periventricular hypothalamus, mesencephalic laminar nucleus, nucleus nervi terminalis and retina (presumed amacrine cells), and along the olfactory nerves. FMRF-IR fibers were distributed throughout the brain with highest densities in the ventral area of the telencephalon, in the medial forebrain bundle, and at the borders between layers III/IV and IV/V in the optic tectum. High densities of immunoreactive fibers were also observed in the area around the torus semicircularis, in the medial hypothalamus, median raphe, ventromedial tegmentum, and central gray. In the retina, immunopositive fibers were localized to the inner plexiform layer, but several fiber elements were also found in the outer plexiform layer. The olfactory system displayed FMRF-IR fibers in the epithelium and along the olfactory nerves. These findings differ from those reported in other species as follows: (i) FMRF-IR cells in the retina have not previously been reported in teleosts; (ii) the presence of FMRF-IR fibers in the outer plexiform layer of the retina is a new finding for any species; (iii) the occurrence of immunopositive cells in the mesencephalic laminar nucleus has to our knowledge not been demonstrated previously.

Amino Acid Sequence↗
PubMed1990

Multiple site optical recording of transmembrane voltage (MSORTV), single-unit recordings, and evoked field potentials from the olfactory bulb of skate (Raja erinacea).

1. Multiple site optical recording of transmembrane voltage (MSORTV), together with conventional extracellular electrophysiological techniques were utilized with in vivo and in vitro preparations of the olfactory bulb of the Atlantic skate Raja erinacea to analyze electrical activity simultaneously in layers deep to the glomerular layer. 2. In the living animals and the in vitro isolated olfactory bulb, orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by a series of early field-potential waves (N1, P1, N2, P2, N3, and N4). During paired stimulation experiments, unusual patterns of facilitation and suppression were observed for the N2 wave. 3. After orthodromic stimulation, single units, presumably mitral/tufted cells, exhibited a period of early discharge, followed by a period of suppression of spontaneous activity and of their test response in a pair stimulation paradigm. Some neurons also exhibited a labile period of reexcitation that was accompanied by a late surface negative field potential; these responses were also present in olfactory bulb slices. 4. Extrinsic absorption changes obtained from 500-microns saggital slices of the olfactory bulb, stained with the pyrazooxonal dye RH-155, consisted mainly of two types of depolarizing responses, a fast and a slow component, followed under some conditions by a late hyperpolarization. All signals exhibited wavelength dependences typical of the action spectrum of RH-155 and were abolished in the presence of tetrodotoxin (TTX) or high K+ in the bath. 5. The fast component of the optical signal represents synchronous compound action potentials conducted by the olfactory nerve fibers or evoked in the mitral/tufted somata and axonal pathways. The slow depolarizing optical signal appeared, after orthodromic stimuli, mainly in the zone between the glomeruli and the mitral/tufted layer; barium (1-10 mM), which depolarizes glial cells, increased its size and duration, suggesting that this signal does not reflect a glial response to [K+]o. 6. Different condition/test (C/T) intervals produced partial or complete suppression of the test response, depending on the recording site and the stimulus intensity. Just threshold orthodromic stimuli evoked an intermediate period of facilitation of the slow signals. A similar period was also observed in the N2 wave of the field potential. 7. Calcium channel blockers such as cadmium ion, or a low Ca2+ medium, suppressed the slow optical component whether evoked by orthodromic, antidromic, or direct stimulation. gamma-Aminobutyric acid (GABA) and baclofen also reduced or blocked the slow component of the extrinsic absorption signal.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

Chemosensory event-related potentials in response to trigeminal and olfactory stimulation in idiopathic Parkinson's disease.

Decrease of olfactory function in patients with Parkinson's disease (PD) has been reported by several authors. The current study investigated olfaction in PD patients using olfactory event-related potentials (OERPs) as an electrophysiologic correlate of olfactory function in combination with psychophysical testing. A specific focus was the influence of antiparkinsonian drugs. We investigated PD patients treated with antiparkinsonian drugs (n = 13) and PD patients who received no pharmacologic treatment (n = 18). They were compared to age- and sex-matched control subjects (n = 38). To obtain OERPs, stimulants were chosen to stimulate specifically the olfactory nerve (2.1 ppm vanillin, 0.8 ppm H2S). In addition, chemosomatosensory event-related potentials were recorded after trigeminal stimulation with 52% v/v CO2. Moreover, the subjects' ability to identify and to discriminate odorants was tested by means of a "squeeze bottle" technique. The study yielded the following major results: (1) Odor identification was impaired in PD patients. It was not influenced by treatment with antiparkinsonian drugs. (2) The OERP latencies were prolonged in both PD patients taking and not taking antiparkinsonian drugs; however, this effect was more pronounced in PD patients taking antiparkinsonian drugs. (3) The intranasal chemosensory trigeminal system seemingly was neither affected by the neuronal degeneration seen in PD nor by treatment with antiparkinsonian drugs.

Adult↗
PubMed1995

Expression of the proteolipid protein gene in glial cells of the post-natal peripheral nervous system of rodents.

The proteolipid protein (PLP) gene encodes for two proteins, PLP and DM-20, which are produced by alternative splicing of exon 3B. PLP is the major CNS myelin protein and is postulated to play a structural role at the intraperiod line. Its developmental expression mirrors that of CNS myelination. DM-20 predominates in the embryo and prior to myelination of the CNS and may be involved in glial cell development. The PLP gene is expressed in the PNS in which DM-20 is the predominant isoform at all ages. In this study we describe the localization of the two isoforms in the post-natal rodent PNS using immunostaining and reverse transcriptase PCR. DM-20 is present in relatively high abundance in non-myelin-forming Schwann cells and within cytoplasmic regions of myelinated internodes, particularly the paranodes and Schmidt-Lanterman incisures and also the outer Schwann cytoplasm and perinuclear cytoplasm. DM-20 is also located in the perineuronal satellite cells of spinal, cranial and autonomic ganglia and in the ensheathing cells of the olfactory nerve layer of the olfactory bulb. PLP was detected by immunocytochemistry in the perinuclear region of myelinated internodes; PCR analysis indicated small amounts of PLP mRNA in the other locations but protein was not detected by immunostaining. Neither protein was identified in compact myelin of the PNS. DM-20 is the predominant product of the PLP gene expressed in a wide variety of peripheral glia. Its presence is not correlated to a myelin-forming state. Other studies have demonstrated early embryonic expression of the PLP gene throughout the PNS and all these features support the hypothesis that any putative role for DM-20 is unrelated to myelination but may involve glial cell development.

Animals↗
PubMed1987

Vestibular, olfactory, and vibratory responses of nucleus basalis prosencephali neurons in pigeons.

Evoked multiple unit responses were recorded through chronically implanted electrodes from the nucleus basalis prosencephali of the pigeon (Columba livia) upon vibratory stimulation of the beak-tip and airborne auditory stimulation, thus confirming earlier anatomical and physiological findings. Electrical stimulation of the olfactory nerve led to similar short latency responses. A specific directional sensitivity to rotatory vestibular stimulation was observed. Pitch motions of the head in the downward direction evoked the most pronounced multi-unit responses. These results support the suggestion that the nucleus basalis prosencephali is a sensorimotor coordinator of the pigeon's pecking/feeding behaviour.

Acoustic Stimulation↗
PubMed1985

Intracellular potentials of salamander mitral/tufted neurons in response to odor stimulation.

Intracellular responses of salamander mitral/tufted neurons to defined odor pulses are described. Responses to odor stimulation, which generally are more complex than responses to olfactory nerve or tract electrical stimulation, show periods of depolarization and hyperpolarization that are influenced by odor concentration and quality. The way these periods coincide with different types of spike patterns in individual cells supports the hypothesis that the temporal patterning of odor responses is generated by differential activation of bulbar circuits.

Animals↗
PubMed1992

Dendritic origin of late events in optical recordings from salamander olfactory bulb.

1. Optical recordings of membrane-potential changes were used to characterize the origin and properties of the electrical signals from the dendritic level in slices of the salamander olfactory bulb. 2. The optical events were correlated with field-potential waves recorded simultaneously. Both responses exhibited patterns similar to those found in other species. 3. Orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by two additional principal waves (N1 and N2). These field-potential waves reflected excitatory postsynaptic potentials at the primary mitral/tufted and granule cell dendrites, respectively. 4. Extrinsic optical signals from horizontal slices stained with the pyrazo-oxonal dye RH-155 showed a characteristic sequence of depolarizing and hyperpolarizing events. All of the signals exhibited a wavelength dependence expected for this dye and were abolished in the presence of high K+ in the bath. 5. According to their time courses, depolarizing responses under normal recording conditions were divided into two components, fast and slow. Orthodromic stimuli evoked a fast presynaptic response that represents synchronous compound action potentials from olfactory nerve fibers. At subglomerular levels, additional fast responses could often be recorded at the peri/subglomerular level and in the mitral/tufted somata region. These postsynaptic responses partially coincided with the rising phase of a different depolarizing signal, a slow component characterized by its prolonged time course. 6. With orthodromic stimulation, this slow signal attained its largest amplitude in the zone between the glomeruli and the superficial part of the external plexiform layer (EPL). Antidromic stimuli evoked a signal with some similarities to the one evoked orthodromically, but originating in deeper EPL regions. 7. Slow components were characterized by their Ca dependence. Low Ca2+ medium, or calcium channel blockers, suppressed this optical component, whether evoked orthodromically, antidromically, or by direct stimulation. In addition, Ba2+ (2.5-3.6 mM) in the bath did not abolish these responses, suggesting that they do not reflect a glial depolarization in response to elevated extracellular K+ concentration ([K+]o). 8. Locally applied stimuli next to the glomerular layer elicited these signals in 5-10 microM tetrodotoxin (TTX) or in low extracellular Na+ concentration ([Na+]o) medium, but antidromic or orthodromic stimuli failed to evoke the response under these conditions. The sizes of the responses to local stimuli remained constant, but an increase in their duration was observed in either TTX or low [Na+]o. 9. gamma-Aminobutyric acid (GABA) and baclofen reduced the size of the slow components in a dose-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1981

Neuronal and glial release of [3H]GABA from the rat olfactory bulb.

GABA uptake and release mechanisms have been shown for neuronal as well as glial cells. To explore further neuronal versus glial components of the [3H]gamma-aminobutyric acid ([3H]GABA) release studies were performed with two different microdissected layers of the olfactory bulb of the rat: the olfactory nerve layer (ONL), consisting mainly of glial cells, and the external plexiform layer (EPL) with a high density of GABAergic dendritic terminals. In some experiments substantia nigra was used as a GABAergic axonal system and the trigeminal ganglia as a peripheral glial model. Spontaneous release of [3H]GABA was always lower in neuronal elements as compared with glial cells. A veratridine-evoked release was observed from the ONL but not from the trigeminal ganglia. Tetrodotoxin (TTX) abolished the veratridine-evoked release from the ONL, which also showed a partial inhibition when high magnesium concentrations were used in a Ca2+-free solution. beta-Alanine was strongly exchanged with [3H]GABA from the ONL of animals with the olfactory nerve lesioned and from animals with no lesion; but only a small heteroexchange was found from the external plexiform layer. The beta-alanine heteroexchange was able to deplete the releasable GABA store from the ONL of lesioned animals. In nonlesioned animals and the external plexiform layer, the veratridine-stimulated release of [3H]GABA was not significantly reduced after the beta-alanine heteroexchange. Stimulation of the [3H]GABA release by high concentrations of potassium elicited a higher release rate from axonal terminals than from dendrites or glia. Neurones and glia showed a similar inhibition of [3H]GABA release when a high magnesium concentration was added to a calcium-free solution. When D-600 was used as a calcium-flux blocker no inhibition of the release was observed in glial cells, whereas an almost complete blockage was found in both neuronal preparations (substantia nigra and EPL). These results provide further evidence for differential release mechanisms of GABA from CNS neurones and glial cells.

Aminobutyrates↗
PubMed1993

Synaptophysin and synaptoporin expression in the developing rat olfactory system.

The expressions of two closely related synaptic vesicle antigens synaptophysin and synaptoporin were examined in the olfactory system of the adult rat and during pre- and postnatal development. In the adult, immunocytochemistry showed that the continuously regenerating olfactory receptor neurons (primary neurons) produce both synaptophysin and synaptoporin which were localized in the cell bodies of the receptor neurons in the olfactory epithelium, their dendrites, axonal processes in the olfactory nerve and their terminals in the olfactory bulb glomeruli. Furthermore, ultrastructural analysis revealed synaptophysin- and synaptoporin-immunoreactivities associated with synaptic vesicles in most olfactory receptor axonal terminals impinging on dendrites of the mitral and tufted neurons (secondary neurons in the olfactory bulb circuitry) in the olfactory glomeruli. In like manner, tufted neurons, granule and periglomerular neurons (interneurons in the olfactory bulb circuitry) express both synaptophysin and synaptoporin. In contrast, mitral neurons expressed only the synaptophysin antigen which was likewise associated with mitral axonal terminals in their target the olfactory cortex. The patterns of synaptophysin and synaptoporin expressions in mitral neurons (synaptophysin only) and tufted neurons (synaptophysin and synaptoporin) were similar in prenatal, postnatal and adult rats as revealed by immunocytochemistry and in situ hybridization. However, the biosynthesis of synaptophysin and synaptoporin by granule and periglomerular neurons, olfactory bulb interneurons, occurred mainly postnatally.

Animals↗