Neurons Of Rat Cerebral Cortex Research Articles

Bromide, in the therapeutic concentration, enhances GABA-activated currents in cultured neurons of rat cerebral cortex

We investigated the effect of bromide on γ-aminobutyric acid (GABA)-activated currents in cultured cerebral neurons of the rat, employing whole-cell voltage- and current-clamp techniques. Application of 100 μM GABA elicited currents whose reversal potential was 0 mV with equal concentrations of chloride in both pipette and bath solutions and more negative than −60 mV with 159 mM chloride extracellularly and 4 mM chloride inside. Bicuculline blocked the currents. These findings showed that the currents were composed of chloride flux through GABA A receptor-coupled channels. Reversal potential revealed a permeability ratio of bromide with respect to chloride ( P Br / P Cl ) of 1.51. When 100 μM GABA was applied with the extracellular solution containing 140 mM bromide and 19 mM chloride, the currents were enhanced 2.00- and 1.91-fold at the holding potentials of t-20 mV and 0 mV, respectively. Extracellular solutions containing various concentrations of bromide substituted for the same amount of chloride were applied with 100μM GABA. The therapeutic concentration of 1C mM and 20 mM bromide enhanced the currents 1.28- and 1.36-fold of the control currents at the holding potential of-t 20 mV, respectively. Under current-clamp recording, a larger hyperpolarization was obtained by the application of GABA with a 140 mM bromide-containing solution. These findings suggest that bromide potentiated GABA-activated currents at the therapeutic concentrations ranging from 10 mM to 20 mM, causing the larger GABA-induced hyperpolarization. It is postulated that the antiepileptic effect of bromide might occur through the potentiation of inhibitory postsynaptic potentials elicited by GABA.

Differential assembly of coexpressed glutamate receptor subunits in neurons of rat cerebral cortex

In the rat, subunits of the glutamate receptor family fall into three pharmacologically distinct groups: alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid preferring receptors (Glu R1-4), kainate preferring receptors (Glu R5-7, KA 1, KA 2), and N-methyl-D-aspartate preferring receptors (NMDA R1, NMDA R2A-2D). In the present study, we demonstrate immunocytochemically that the majority of neurons in rat cerebral cortex coexpress members of all three groups of glutamate receptor subunits, Glu R2/3, Glu R5/6/7, and NMDA R1. Using immunoaffinity purified or immunoprecipitated alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, kainate and N-methyl-D-aspartate receptors, we show that alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors containing Glu R1-4, kainate receptors containing Glu R6, Glu R7, and KA 2 and N-methyl-D-aspartate receptors containing NMDA R1 each form distinct protein complexes that do not share subunits. Our data indicate that a mechanism exists which allows for the specific assembly of selected glutamate receptor subunits into functionally and structurally distinct heteromeric receptors.

Development of GABAergic non-pyramidal neurons in the rat cerebral cortex

Development of GABAergic non-pyramidal neurons in the rat cerebral cortex

Neurons in rat cerebral cortex that synthesize nitric oxide: NADPH diaphorase histochemistry, NOS immunocytochemistry, and colocalization with GABA

Neurons that stain for NADPH diaphorase, which colocalizes with nitric oxide synthase (NOS), are scattered uniformly across neocortex, and denser in entorhinal cortex. In the primary sensorimotor cortex, 0.5–2% of neurons contain NOS. These are most numerous in layers II–III, whereas NOS-positive fibers are concentrated in layers IV and VI. Most stained neurons are aspiny bipolar cells. Some in deep layers are multipolar; very few are pyramidal-shaped. In layer IV, NOS-positive neurons and their dendrites are confined to the septa between barrels. Retrograde tracing experiments demonstrate that NOS-positive cells are local circuit neurons. Double staining demonstrates that NOS-positive neurons also contain GABA.

Expression of non-adrenergic imidazoline sites in rat cerebral cortical astrocytes.

Clonidine and related imidazoline agents, beside binding to alpha 2-adrenergic receptors, have been shown to bind to a non-adrenergic site (imidazoline sites) in brain and peripheral tissues. However, which cell types in brain, namely neurons or glia, express this binding site and the cellular effects of activation of this site are not known. We investigated the cellular localization of imidazoline binding sites in cultured rat cortical astrocytes and neurons. Membranes prepared from cultured astrocytes showed specific, high affinity binding (KD: 4 nM) for 3H-idazoxan with about tenfold higher number of binding sites than alpha 2-adrenergic sites (Bmax: 220 vs. 20 fmol/mg protein). Displacement studies exhibited the rank order of potency: cirazoline > idazoxan > amiloride > clonidine >>> epinephrine = ruawolscine defining this site as I-2a subtype of imidazoline binding sites. Moreover, the binding was inhibited by K+ but not by Na+, another characteristic of imidazoline binding sites. In contrast, membranes prepared from cultured neurons showed fewer binding sites for 3H-idazoxan that were completely displayed by adrenergic agents. Incubation of astrocytes with idazoxan, but not rauwolscine, resulted in a concentration-dependent increase in the levels of mRNA for the astrocyte specific molecule glial fibrillary acidic protein. We conclude that (a) the non-adrenergic imidazoline binding sites are expressed in astrocytes but not in neurons in rat cerebral cortex and (b) these "receptors" may influence astrocyte physiology by regulating the levels of GFAP.

O-375 - Facilitatory effect of docosahexaenoic acid on NMDA receptor response in pyramidal neurons of rat cerebral cortex.

O-375 - Facilitatory effect of docosahexaenoic acid on NMDA receptor response in pyramidal neurons of rat cerebral cortex.

Functional and morphological changes in cultured neurons of rat cerebral cortex induced by long-term application of aluminum

Aluminum is an environmental neurotoxin and a suspected risk factor for Alzheimer's disease. The neurotoxicity of aluminum on cultured neurons of rat cerebral cortex was investigated using an assay system for synapse formation and immunohistochemistry. The frequency of spontaneous oscillations of intracellular Ca 2+, which is correlated to the number of synapses, was decreased after exposure to 100 μM of aluminum chloride for 22 days. Long-term application of aluminum (48 days) caused aggregation of cell bodies and fasciculation of processes. Processes and cell bodies were strongly stained by antibody to tau protein, which is one of the main components of Alzheimer's neurofibrillary tangles. It is suggested that the characteristics of the degeneration of cultured neurons induced by aluminum show some similarities to the pathology observed in brains with Alzheimer's disease.

Zonisamide blocks T-type calcium channel in cultured neurons of rat cerebral cortex

We investigated the effect of zonisamide, a new antiepileptic drug, on voltage-dependent Ca 2+ currents in cultured neurons of rat cerebral cortex. Whole-cell voltage-clamp recordings demonstrated at least two distinct voltage-dependent Ca 2+ currents: 1. (1) a lowthreshold, rapidly inactivating component, T-type Ca 2+ current, which is sensitive to 100,μM Ni 2+, and 2. (2) a high-threshold, slowly inactivating (long-lasting) component, L-type Ca 2+ current. Zonisamide, a new anticonvulsant effective against maximal electroshock (MES) seizures in mice reduced T-type Ca 2+ current in a dose-dependent manner. The mean percentage of reduction was 59.5 ± 7.2% at 500 μM, but zonisamide had no effect on L-type Ca 2+ current. A methylated analog of zonisamide, which is ineffective against MES seizures in mice, was tested at a concentration of 500 μM, and reduced neither T-type nor L-type Ca 2+ current. These findings suggest that the effects of zonisamide against MES seizures might occur through the reduction of T-type Ca 2+ current. Because drugs that are effective against MES seizures are thought to prevent seizure discharge spread, T-type Ca 2+ channels could underlie a cellular mechanism of spreading activity in epileptic seizures.

P-398 - Muscarinic acetylcholine response in pyramidal neurons of rat cerebral cortex

P-398 - Muscarinic acetylcholine response in pyramidal neurons of rat cerebral cortex

Functional and morphological changes of cultured neurons of rat cerebral cortex induced by aluminum: Possible relationship to Alzheimer's disease: M. Kawahara, M. Ichikawa ∗,K. Kobayashi, K. Muramoto, Y. Kuroda Departments of Molecular & Cellular Neurobiology, and Anatomy & Embryology ∗; Tokyo Metropolitan Institute for Neuroscience, Musashidai 2-6, Fuchu-city, Tokyo 183, Japan

Functional and morphological changes of cultured neurons of rat cerebral cortex induced by aluminum: Possible relationship to Alzheimer's disease: M. Kawahara, M. Ichikawa ∗,K. Kobayashi, K. Muramoto, Y. Kuroda Departments of Molecular & Cellular Neurobiology, and Anatomy & Embryology ∗; Tokyo Metropolitan Institute for Neuroscience, Musashidai 2-6, Fuchu-city, Tokyo 183, Japan

Properties of single fast chloride channels from rat cerebral cortex neurons.

1. Properties of Cl- channels from surface membranes of acutely dissociated rat cerebral cortical neurons were studied with the patch clamp technique. These channels were present in the majority of excised inside-out membrane patches. 2. Cl- channels were rarely observed in cell-attached membrane patches, and usually several minutes elapsed following excision of the patch before Cl- channels became active. 3. Under asymmetric ionic conditions (1000 mM-KCli, 140 mM-KClo), neuronal Cl- channels are fairly selective for Cl- over K+ and Na+, with permeability ratios, determined by reversal potential shifts of 4.8 for both PCl/PK and PCl/PNa. 4. Neuronal Cl- channel kinetic activity remained stable over periods of time long enough to collect up to 500,000 open and closed intervals. Occasionally, the channels entered altered modes of activity. In the 'buzz mode' the open and closed interval durations became much shorter than normal for several hundreds of intervals. In the 'subconductance mode' the channel opened to a current level about two-thirds of the normal level. 5. Using the method of maximum likelihood, sums of exponentials were fitted to the distributions of open and closed interval durations. Open interval distributions required at least two exponential components with time constants of less than 1 ms. At least six or seven exponential components were required to fit the closed interval distributions with time constants ranging from 30 microseconds to several hundreds of milliseconds. This suggests that neuronal Cl- channels enter at least two open and six or seven closed kinetic states during normal activity. 6. Cl- channels often entered long-duration closed states of several minutes which could not be accounted for by the sums of exponentials fitted to the distribution of closed interval durations. 7. Neuronal Cl- channels exhibit a marked voltage dependence with the percentage of time the channels are open increasing with depolarization. Most of the observed voltage dependence can be accounted for by a decrease in the mean closed interval duration with depolarization. The mean open interval was relatively independent of voltage. 8. These results suggest a high degree of similarity in kinetic behaviour and conductance properties between the fast Cl- channels of tissue-cultured rat skeletal muscle and fast Cl- channels in acutely dissociated rat cerebral cortical neurons.

Functional and morphological changes of cultured neurons of rat cerebral cortex induced by aluminium: Relationship to Alzheimer's disease

Functional and morphological changes of cultured neurons of rat cerebral cortex induced by aluminium: Relationship to Alzheimer's disease

A muscle-derived factor(s) induces expression of a catecholamine phenotype in neurons of cultured rat cerebral cortex

We sought to determine the source of the signal(s) that promotes expression of the catecholamine (CA) enzyme tyrosine hydroxylase (TH) in cultured neurons of embryonic rat cerebral cortex, a tissue which is not thought to contain CA cells in vivo. Cortical neurons were cultured with their non-neuronal constituents and 48 hr later immunostained for TH. Fibroblasts or glia had no effects, however, blood vessels increased the numbers of TH neurons nearly 4-fold. Coculture with either perinatal aorta, skeletal or cardiac muscle, clonal muscle cell lines 1440 (smooth) and L6 (skeletal), conditioned media from L6 cells, or a soluble extract of L6 cells increased the number of TH neurons up to 20-fold. The induction of TH by muscle extract was (1) dose dependent; (2) paralleled by a proportional increase in the steady-state levels of TH mRNA; (3) greatly reduced by the RNA synthesis inhibitor alpha-amanitin or the protein synthesis inhibitor cycloheximide; and (4) unassociated with change in the survival of neurons in culture. The response was not replicated by treatment with other established neurotrophic substances, including NGF, EGF, FGF, PDGF, neuroleukin, insulin, pyruvate, KCI, adenosine, or inosine. We conclude that muscle contains a potentially novel substance, muscle-derived differentiation factor (MDF) that promotes differentiation but not survival of neurons of cerebral cortex by de novo synthesis of TH mRNA and TH protein. Thus, neurons of the CNS, as in periphery, may undergo phenotypic interconversion in response to biologically derived molecules in their environment.

Immunocytochemical relationship between mesocortical dopaminergic nerve terminals and neuropeptide Y-containing neurons in rat cerebral cortex

Immunocytochemical relationship between mesocortical dopaminergic nerve terminals and neuropeptide Y-containing neurons in rat cerebral cortex

In vitro synapse formation among cultured neurons of rat cerebral cortex: Kazuyo Muramoto, Kazuo Kobayashi and Yoichiro Kuroda, Department of Neurochemistry, Tokyo-Metropolitan Institute for Neurosciences, 2-6 Musashidai, Fuchu-shi, Tokyo 183, Japan

In vitro synapse formation among cultured neurons of rat cerebral cortex: Kazuyo Muramoto, Kazuo Kobayashi and Yoichiro Kuroda, Department of Neurochemistry, Tokyo-Metropolitan Institute for Neurosciences, 2-6 Musashidai, Fuchu-shi, Tokyo 183, Japan

Effect of ginseng saponins on the survival of cerebral cortex neurons in cell cultures.

The effects of nerve growth factor (NGF) and saponins isolated from Panax ginseng C.A. Mayer on the survival of chick and rat embryonic cerebral cortex neurons were examined. Ginsenoside Rg1 (GRg1) exerted a survival-promoting effect on both chick and rat cerebral cortex neurons in cell cultures. Ginsenoside Rb1 (GRb1) also had an effect in the rat and displayed some influence in the chick. NGF alone exerted no effect on both neurons, although it did potentiate the GRb1 effect on chick embryonic cerebral cortex neurons, but did not alter the GRb1 effect on rat embryonic cerebral cortex neurons. NGF did not alter the survival-promoting effect of GRg1 on either chick or rat embryonic cerebral cortex neurons. The other saponins alone or with NGF exerted no effect on the survival of cerebral cortex neurons in either the chick or rat.

Variations in DNA topoisomerase I activity after gamma irradiation of mature neurons

The activity of DNA topoisomerase I in nuclear extracts from rat cerebral cortex neurons increases about two-fold after gamma irradiation (700 rads) of rats or incubated cerebral cortex slices. Analysis of the salt dependence of the DNA topoisomerase I association with chromatin shows a change of the activity only for tight-bound pool of the enzyme. The change appears to reflect a modification of the enzyme which results from its repair function.

Differential acetylation of core histones in rat cerebral cortex neurons during development and aging

Core histones can be modified by aceylation and this modification has been correlated with the modulation of chromatin condensation and histone deposition. We have now studied the levels of acetylation of the core histones in rat brain cortical neurons from the middle of the period of neuronal proliferation through postnatal development and aging. The results show that the level of acetylation of H4 decreases with age. The kinetics of H4 deacetylation show a perinatal fast phase followed by a much slower phase that spans the rest of the period examined. H4 deacetylation is accounted for by the decrease of the monoacetylated species, the proportions of the more highly acetylated species remaining essentially constant. By contrast to histone H4, the overall levels of acetylation and the proportions of the different acetylated species of H2A, H2B and H3 remain unchanged throughout the period examined. Furthermore, the variants belonging to a given histone class always show the same level of acetylation. The fact that in neurons the level of monoacetylated H4 decreases during development and aging, in sharp contrast with the constancy of the levels of all other acetylated histone species, raises the possibility that in interphase chromatin monoacetylated H4 may have a central role in the modulation of chromatin structure. The results also suggest that the slow decrease of the proportion of monoacetylated H4 may imply a gradual loss of chromatin structural plasticity and thus lead to aging.

Functional synapse formation between cultured neurons of rat cerebral cortex. Block by a protein kinase inhibitor which does not permeate the cell membrane.

Functional synapse formation between cultured neurons of rat cerebral cortex. Block by a protein kinase inhibitor which does not permeate the cell membrane.

Intracellular recordings from neurones in rat cerebral cortex during hypoxia.

Neurones in rat hippocampal cortex were exposed to hypoxia while their membrane properties and responses to different kinds of stimuli were recorded with an intracellular electrode. The initial changes consisted of a small depolarization followed by a hyperpolarization. Following these early events the neurones lost their membrane potential through a large depolarization. Similar changes were observed in neurones where the Na/K-ATPase was blocked by ouabain. Responses to direct application of the transmitters GABA and glutamate, which was lost at this point, were restored by passive reestablishment of the membrane potential with current through the intracellular electrode.