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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a recent study of the cat visual cortex, it was shown that there are interindividual differences in the numerical density (Nv) of symmetrical synapses associated with flat vesicles (FS synapses) but not of asymmetrical synapses associated with round vesicles (RA synapses). Since many of the environment-sensitive properties of visual cortex neurons are GABA-dependent, it was suggested that the interindividual differences in FS synapses might be due to environmental factors. To verify this possibility we estimated the Nv of both types of synapses in two groups of six cats, paired by litter and by sex, and raised either in isolation or in a colony from the time of weaning to the age of 8 months. We also measured the Nv of neurons and the thickness of the cortex and made some gross anatomical measurements. The brains of animals raised in the enriched environment are 7% heavier, and their total body weight is 10% greater: The brain-to-body-weight ratio remains unchanged. The total length of the brain is not affected, but the length and width of the cerebral hemispheres are each 5% greater in the enriched cats. As in comparable rat studies, the thickness of the cortex is 4% greater, but in the present study this difference is not significant. The numerical density of neurons is diminished by 17% in enriched animals. This is probably due to a wider separation of neuronal cell bodies in a larger cortical volume, rather than to a loss of neurons. There are no significant changes in the numerical density of RA synapses between the two milieux, but there are nearly twice as many FS synapses per mm3 of tissue in the impoverished cortex. The coefficient of variation of FS synapses, which in the previous study was on the order of 30%, has been reduced to 10% and 7% in enriched and impoverished cats, respectively. We conclude that environmental conditions can lead to selective interindividual differences in the Nv of FS synapses, as seen in our previous study of animals whose rearing conditions were not controlled. The average diameter of RA synaptic profiles is not affected by the environment but FS synapses are 25% wider in the enriched animals. Because of the smaller neuronal Nv in enriched animals, there are, in fact, 18% more RA synapses and 34% fewer FS synapses per neuron in the enriched condition.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of the richness of the environment on the cat visual cortex. 343 78

The distribution of GABA-immunoreactive neurons and axonal varicosities was investigated in the hippocampal region of the rat brain by means of an indirect peroxidase immunocytochemical method with recently developed anti-GABA antibodies. The immunolabeling was found to be restricted to nervous structures: neuronal cell bodies, dendrites and axon terminals. Myelinated axons showing GABA-immunoreactivity were also observed. GABA-immunoreactive neurons were found in great number in the stratum pyramidale, the superficial part of the stratum oriens and the deep part of the stratum radiatum in the Ammon's horn. Less were found in the other regions; rare labeled cells were observed in the superficial part of the stratum radiatum and the middle part of the stratum oriens. The dentate gyrus exhibited numerous labeled cells in the granular layer, few in the hilus, rare in the molecular layer. A high density of GABA-immunoreactive terminals was found at the limit of the stratum oriens with the alveus, in the stratum pyramidale and in the stratum lacunosum. A lower density of labeled fibers was observed in the other areas. The somata and proximal dendrites of pyramidal and granular cells were encompassed by characteristic pericellular arrangements of GABA-immunoreactive varicosities. Ultrastructural observations revealed a diffuse immunoreaction product spread over the cytoplasm and the nucleus without specific relationship with the organelles, and immunoreactive aggregates in the cytoplasm. Labeled dendrites often showed enlargements displaying the immunoreaction whereas thinner segments were devoid of it. They received numerous asymmetrical synapses from unlabeled axon terminals. GABA-immunoreactive terminals were filled with small clear vesicles with immunopositive membranes and were observed in symmetrical contact with somata and dendrites.
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PMID:Gamma-aminobutyric acid-immunoreactivity in the rat hippocampus. A light and electron microscopic study with anti-GABA antibodies. 351 33

The fine structure and types of contact made by GABAergic elements in the septal nuclei were studied at the electronmicroscopic level by means of peroxidase immunocytochemistry, using anti-GABA antibodies. Observations were made on normal and colchicine-injected rats. GABA-immunoreactivity was distributed within somata, dendrites, axonal varicosities and terminals, and myelinated axons. The peroxidase reaction product was diffuse in the cytoplasm; cytoplasmic organelles were generally devoid of immunoreactivity, while showing a strong reaction on the outer surface of their membrane. GABA-immunoreactive (GABA-I) neurons were small (10 microns on average) to medium (20 microns) in size, with round or multipolar cell bodies. Additionally, labeled large (30 microns) cells were observed within the myelinated fibers of the medial septal nucleus after intraseptal administration of colchicine. No difference in the ultrastructural features and distribution of the immunoreactivity of the 2 kinds of cell was noticed, except for a higher number of synaptic contacts on large neurons of the medial septum. GABA-I cells of the medial and lateral nuclei received synapses on their soma and dendrites, made by both immunonegative and GABA-I terminals. Nonimmunoreactive boutons contacting GABA-I cell bodies were of 2 types: those containing small, clear synaptic vesicles and those that additionally contained large dense vesicles. Synaptic vesicles of GABA-I boutons were rarely labeled internally, but showed varying electron densities. Synapses made by GABA-I boutons on GABA-I or unlabeled somata and dendrites were always of symmetrical type. Synapses made by non-GABA-I boutons on GABA-I cells were either symmetrical or asymmetrical.
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PMID:An ultrastructural study of GABA-immunoreactive neurons and terminals in the septum of the rat. 354 51

GABAergic neuronal profiles in the supraoptic nucleus of the rat were immunohistochemically identified by using a purified GABA antibody with the peroxidase-antiperoxidase method. The localization of GABA-like immunoreactivity in nerve terminals on the neurosecretory neurons was examined electron microscopically. A few small GABAergic neurons were found inside the supraoptic nucleus while only a very few medium-sized ones were detected in the perinuclear zone. Intrinsic, non-GABAergic small neurons covered by GABAergic neuropil were also detected. The neuropil with GABAergic axo-somatic synapses evenly encompassed unlabeled neurosecretory perikarya throughout the supraoptic nucleus. The GABAergic system seems to inhibit both vasopressin and oxytocin cells. In this area, glia cells showed clear outlines of unlabeled somata around counter-stained nuclei. Blood capillaries in the supraoptic nucleus were only slightly covered with a GABAergic neuropil. Electron microscopic observations demonstrated the presence of GABAergic axo-somatic symmetrical and axo-dendritic asymmetrical synapses on the neurosecretory neurons. GABA-like immunoreactivity was localized on the membranes of microtubules and synaptic vesicles, on the external membranes of the mitochondria, and on the inner leaf of the presynaptic sites. Numerous pairs of non-immunoreactive synapses were arranged along these immunoreactive synapses.
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PMID:Immunohistochemical studies on the GABAergic system in the rat supraoptic nucleus using the PAP method with an application of electron microscopy. 355 72

In halothane-anaesthetized cats implanted with several push-pull cannulae the release of dopamine from nerve terminals and dendrites of the two nigrostriatal dopaminergic pathways is shown to be asymmetrically or symmetrically regulated bilaterally when dopaminergic or GABAergic drugs are infused into one side of the nigra. Nigrothalamic GABAergic neurons may intervene in the asymmetrical regulation, as sagittal section of the thalamic massa intermedia blocks the contralateral effects induced by dopaminergic drugs. The role of thalamic nuclei in the bilateral regulation of dopamine and GABA release in the caudate nucleus and substantia nigra is further demonstrated by studies showing that (1) electrical stimulation of thalamic motor nuclei induces bilateral asymmetrical changes in dopamine release resembling the changes evoked by unilateral sensory stimuli or stimulation of cerebellar nuclei; (2) electrical stimulation of intralaminar or some midline thalamic nuclei leads to bilateral (or contralateral) symmetrical changes in dopamine release, some of these effects being comparable to those induced by unilateral stimulation of the motor cortex; (3) unilateral lesions of motor or intralaminar thalamic nuclei reverse the changes in GABA release in the contralateral caudate nucleus or substantia nigra induced by unilateral infusion of muscimol into the nigra; and (4) unilateral infusion of GABA into thalamic motor nuclei induces bilateral symmetrical regulation of dopamine release in caudate nuclei by means of presynaptic facilitatory influences.
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PMID:Role of the thalamus in the bilateral regulation of dopaminergic and GABAergic neurons in the basal ganglia. 609 23

The release of transmitters was studied in various structures of the basal ganglia in cats implanted with several push-pull cannulas. Local depolarization enhanced Met-enkephalin release in the globus pallidus. Activation of striatonigral substance P(SP) neutrons stimulated the transmitter release from terminals. Unilateral electrical stimulation of the caudate nucleus evoked GABA release in both substantia nigrae and pallidoentopeduncular nuclei. The unilateral facilitation or interruption of nigral SP transmission modified dopamine (DA) release in the ipsilateral caudate nucleus in contrast, modifications of GABAergic or glycinergic nigral transmissions induced bilateral symmetrical effects, whereas bilateral asymmetrical changes in DA release in the two caudate nuclei were seen during the unilateral modification of nigral DA transmission. Changes in the dendritic release of DA induced changes in serotonin release both in the substantia nigra and in the ipsilateral caudate nucleus. Finally, it will be shown that acetylcholinesterase can be released from the substantia nigra and the caudate nucleus through processes dependent on nerve activity.
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PMID:In vivo release of transmitters in the cat basal ganglia. 616 43

The contribution of motor and intralaminar thalamic nuclei to the changes of [3H]GABA release evoked in both caudate nuclei (CN) and both substantia nigra (SN) by a unilateral nigral application of muscimol (10(-6) M) was investigated on halothane-anaesthetized cats. Acute lesions were performed on one side of the thalamus at the level of either the ventralis medialis and ventralis lateralis (motor nuclei) or the centralis lateralis and paralamellar zone of the medialis dorsalis (intralaminar nuclei). The release of [3H]GABA neosynthesized from [3H]glutamine was measured by perfusing continuously a [3H]glutamine-enriched physiological medium through a push-pull cannula implanted in the 4 structures under investigation. After two hours of superfusion, muscimol (10(-6) M) was delivered for 60 min through the nigral push-pull cannula implanted ipsilaterally to the thalamic lesion. Evoked changes of [3H]GABA release were analyzed either in motor or intralaminar nuclei lesioned cats and compared to those observed in intact animals. Whatever the localization of the thalamic lesions was, an increased release of [3H]GABA was elicited locally in the SN and distally in the ipsilateral CN as in intact animals, suggesting that the responses induced ipsilaterally did not require nigro-thalamic pathways. On the contrary, in the contralateral CN changes of [3H]GABA release evoked by the nigral muscimol application were reversed by both types of thalamic lesion. Instead of a decreased release of [3H]GABA observed in intact cats, an increased release of [3H]GABA was detected in lesioned animals. In the contralateral SN, the response was reversed only after the intralaminar nuclei lesion. In this situation nigral muscimol application induced a decreased release of [3H]GABA in contrast to the enhanced release observed in intact and motor thalamic lesioned cats. The parallel increased release of [3H]GABA observed in the contralateral CN and SN in motor thalamic nuclei lesioned cats suggests an activation of the striatonigral cells by the nigral muscimol treatment. The asymmetrical changes of [3H]GABA release measured in the contralateral CN and SN in intact and intralaminar nuclei lesioned cats could indicate a presynaptic modulation of the [3H]GABA release acting either at the CN or the SN levels. The possible pathways involved in the interhemispheric transfer of information originating from one SN to the contralateral basal ganglia components are also discussed.
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PMID:In vivo release of [3H]GABA in cat caudate nucleus and substantia nigra. II. Involvement of different thalamic nuclei in the bilateral changes induced by a nigral application of muscimol. 633 70

In halothane anaesthetized cats, a push-pull cannula was implanted into the right caudate nucleus (CN) and in each substantia nigra (SN). The release of [3H]GABA continuously formed from [3H]glutamine was estimated in each structure. Acetylcholine (ACh, 5 x 10(-5) M) added in presence of eserine (5 x 10(-5) M) for 50 min in the right caudate nucleus 2 h after the onset of superfusion with [3H]glutamine, stimulated the [3H]GABA release locally. The effect was biphasic when ACh application was made in the median two-thirds of the structure and it was monophasic and transient when the ACh application was restricted to the lateral part. ACh application in the right caudate nucleus also induced changes in [3H]GABA released in the anterior (pars reticulata) and posterior (pars compacta) parts of both SN. While [3H]GABA release was enhanced in the ipsilateral anterior SN, it was reduced in the contralateral anterior SN. Respective opposite effects were observed in the posterior parts of the ipsi- and contralateral SN. These bilateral asymmetrical changes in [3H]GABA release were not dependent on the site of ACh application in the right caudate nucleus. These results indicate that the facilitation of cholinergic transmission in one caudate nucleus influences in an opposite way the striato-nigral GABA neurones on both sides of the brain.
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PMID:Bilateral asymmetrical changes in the nigral release of [3H]GABA induced by unilateral application of acetylcholine in the cat caudate nucleus. 704 21

In order to clarify the origin and to examine the neurochemistry and synaptology of the projection from the mesopontine tegmentum (MTg) to the subthalamic nucleus (STN), rats received discrete deposits of anterograde tracers in different regions of the MTg. Anterogradely labeled fibers were examined in the light and electron microscopes. The distribution of GABA or glutamate immunoreactivity was examined by post-embedding immunocytochemistry. The anterograde tracing demonstrated that the projection to the STN arises from at least three divisions of the MTg: the area defined by the cholinergic neurons of the pedunculopontine region (PPN-Ch 5), the more medial and largely noncholinergic midbrain extrapyramidal area (MEA) and to a lesser extent the laterodorsal tegmental nucleus (LDTg). Post-embedding immunocytochemistry revealed that there are GABA-immunopositive and immunonegative components to this projection and at least a proportion of the GABA-immunonegative component is enriched in glutamate immunoreactivity. The similarity of the morphology, trajectory and synaptology of the anterogradely labeled fibers and the choline acetyltransferase (ChAT)-immunopositive fibers supports the proposal that at least part of the projection is cholinergic. The terminals anterogradely labeled from the MTg and the ChAT-immunoreactive terminals form asymmetrical synapses with the dendrites and spines of subthalamic neurons. Both anterogradely labeled and ChAT-positive terminals make convergent synaptic contacts with GABA-immunoreactive terminals that form symmetrical synaptic contacts and are probably derived from the globus pallidus. Taken together these findings imply that the MTg sends cholinergic, GABAergic and glutamatergic projections to the STN where at least one of the functional roles is to modulate the indirect pathway of information flow through the basal ganglia that is carried via the pallidosubthalamic projection.
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PMID:Cholinergic, GABAergic, and glutamate-enriched inputs from the mesopontine tegmentum to the subthalamic nucleus in the rat. 747 65

The mitral cell of the olfactory bulb is the primary relay neuron that transmits information from the olfactory receptors to the rest of the brain. This excitatory neuron releases glutamate from presynaptic dendrites and axon terminals. All rat mitral cells studied showed strong, selective, and widespread metabotropic glutamate receptor mGluR1 alpha immunoreactivity on the presynaptic membrane of dendrites, often at the synaptic vesicle release site, when examined with light and electron microscopy. The finding of glutamate receptors on mitral cell secondary dendrites supports the conclusion that not all dendritic membrane with glutamate receptors necessarily have gray type I asymmetrical synaptic specializations. In contrast, the metabotropic glutamate receptor mGluR5 was not found in mitral cells but was expressed by granule cells and astrocytes around mitral dendrites. Both mGluR1 alpha and mGluR5 were expressed early in development, with strong immunostaining present by postnatal day 1. MGluR1 alpha staining at birth mirrored the adult staining pattern. MGluR5 staining at birth showed different patterns of immunostaining than that found in the adult, particularly in the external plexiform layer. In vitro olfactory bulb neurons and their dendrites from embryonic day (E) 18 olfactory bulbs responded to t-ACPD and quisqualate, selective and nonselective metabotropic glutamate receptor agonists, and to several ionotropic glutamate agonists with increases in intracellular Ca2+ as studied with fura-2 digital imaging. These data indicate that the receptors were functionally active at an early stage of development. Application of the glutamate receptor blockers d-2-amino-5-phosphonovalerate (AP5) and 6-cyano-7-nitroquinoxaline (CNQX) to E17 olfactory bulb neurons after only 4 days in vitro resulted in a dramatic decrease in Ca2+ levels in 70% of 128 cells tested, suggesting that embryonic neurons after a short time in vitro can actively secrete glutamate. The presence of glutamate receptors on the long mitral cell dendrite suggests that it would be able to respond to release of its own excitatory transmitter, probably at an early stage of development. In the probable absence of other excitatory input to the secondary mitral dendrites, it would be the only excitatory "input." This autoexcitatory response would be modulated by release of GABA from olfactory interneurons occurring milliseconds after glutamate release induced by olfactory nerve activation. This novel type of neuronal microcircuitry would potentially amplify signal transmission and current spread along the long mitral dendrites and could play an important role in lateral inhibition of olfactory neurons.
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PMID:Presynaptic metabotropic glutamate receptors in adult and developing neurons: autoexcitation in the olfactory bulb. 749 28


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