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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 55 (1984), S. 351-358 
    ISSN: 1432-1106
    Keywords: Excitatory amino acid ; Antagonist ; Gamma-D-glutamylglycine ; Cis-2,3-piperidine dicarboxylate ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The actions of gamma-D-glutamylglycine (DGG) and cis-2,3-piperidine dicarboxylate (PDA) were studied in thin hippocampal sections of the guinea pig by intracellular recording. DGG and PDA suppressed depolarizations induced in CA3 neurons by short pulses of L-aspartate (Asp), D-homocysteat (DH) or L-glutamate (Glu). Asp-and DH-responses were more susceptible to the antagonists than were Glu-responses. The sensitivity difference between Glu-responses and Asp-or DH-responses was not so pronounced that these antagonists could be used to differentiate between Glu-mediated and Asp-mediated synapses. Glu and Asp pulses induced long hyperpolarizing deflections in some neurons. In about half of these neurons, PDA and DGG were without effect on the hyperpolarizing responses. The depolarizing action of gamma-amino butyric acid was unaffected by DGG and PDA. These antagonists blocked excitatory postsynaptic potentials induced by fimbrial stimulation. These results suggest that DGG and PDA are relatively specific antagonists of excitatory amino acids in the hippocampus, and that Glu (or Asp) is the neurotransmitter released from axons of CA3 neurons.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 51 (1983), S. 128-134 
    ISSN: 1432-1106
    Keywords: 2-Amino-4-phosphonobutyric acid ; Hippocampus ; Glutamate receptor ; Mossy fiber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The action of 2-amino-4-phosphonobutyric acid (APB) on mossy fiber-induced excitation in CA3 neurons was studied in vitro with thin sections of guinea pig hippocampus. D- and DL-APB suppressed field potentials induced in regio CA3 by granular layer stimulation. Threshold concentration of DL-APB to induce the suppression was 2–5 μM. D-APB was about 10-fold less potent than DL-APB. Field potentials induced by fimbrial stimulation were much less affected. DL-APB was without effect on antidromic activation of granule cells. 2-Amino-phosphonovaleric acid had a similar but less potent action. Gamma-D-glutamylglycine and cis-2,3-piperidine dicarboxylic acid were almost ineffective. DL-APB suppressed excitatory postsynaptic potentials recorded intracellularly from CA3 neurons in response to granular layer stimulation but caused no marked changes in resting potentials, action potentials and membrane conductance. Single cell discharges induced by iontophoretic administration of glutamate (Glu) or aspartate (Asp) were unaffected when mossy fiber-induced excitation was suppressed by D- or DL-APB. DL-APB had no suppressing action on Glu- or Asp-induced depolarizing potentials. These results indicate that APB is a relatively specific blocker of synaptic transmission between mossy fibers and CA3 neurons, and that this action does not result from blockade of receptors for Glu or Asp.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 41 (1981), S. 264-270 
    ISSN: 1432-1106
    Keywords: Norepinephrine ; Enkephalin ; Catecholamine ; Bed nucleus of the stria terminalis ; Amygdala
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of catecholamines, enkephalins and related compounds on electrical activity of the bed nucleus of stria terminalis (BST) were studied in vitro on thin BST sections prepared from guinea pig brains. Norepinephrine (NE) and epinephrine (E) suppressed field potentials elicited by a single shock to the stria terminalis (ST). The effects of NE and E were mimicked by phenylephrine and blocked by phenoxybenzamine. Isoproterenol and dichloroisoproterenol were without effect. NE and E suppressed the spontaneous firing of BST neurons and discharges elicited by ST stimulation. Dopamine was a less potent depressant. [D-Ala2]-Met-enkephalinamide (EKA) suppressed the field potentials and spike discharges elicited by ST stimulation. Spikes occurring spontaneously or during administration of glutamate were also suppressed by EKA. The action of EKA was blocked by naloxone. Late inhibition induced by stimulation of the lateral division of the ST was blocked by naloxone in about a third of the neurons examined. These results indicate that norepinephrine suppresses the activity of BST neurons by activating postsynaptic α-receptors. It is also suggested that opioid peptides mediate inhibitory control of the amygdala over the BST.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 31 (1978), S. 299-301 
    ISSN: 1432-1106
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 46 (1982), S. 170-176 
    ISSN: 1432-1106
    Keywords: Hippocampus ; Quantal amplitude ; Quantal content ; Mossy fiber ; Frequency potentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The values of quantal content (m) and quantal amplitude (q) of excitatory postsynaptic potentials (EPSPs) elicited in CA3 neurons by activation of granule cells were estimated in thin hippocampal sections maintained in vitro. For this purpose, DL-homocysteate was administered to granule cells, and trains of EPSPs that were typical for single granule cell activation were recorded from individual CA3 neurons. The amplitudes of the first and second EPSPs in each train were measured. From the mean and variance of the amplitudes of the EPSPs, the values of q and m were calculated. The values of m and q for the first EPSPs were estimated at 8.3 and 0.28 mV, respectively, on the average. Potentiation of the second EPSPs was accompanied by a two-fold increase in the values of m without changes in the values of q. Therefore, frequency potentiation in synapses between mossy fibers and CA3 neurons may be explained by an increase in number of released quanta. Amplitudes of EPSPs were found to fluctuate in a manner described by Poisson's law.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 59 (1985), S. 226-231 
    ISSN: 1432-1106
    Keywords: Excitatory amino acid ; Barbiturate ; Glutamate ; Receptor ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The actions of pentobarbital sodium (Pent) on receptors for glutamate (Glu) and related compounds were studied in thin sections of the guinea pig hippocampus. Depolarizations induced by Glu and quisqualate (Quis) in CA3 neurons were reduced in amplitude during iontophoretic administration of Pent. This action of Pent was not accompanied by any noticeable changes in membrane potential or neuron input resistance. Depolarizations induced by N-methyl-D-aspartate were less sensitive to Pent. The fast kainate (KA) response was as susceptible as the Glu response, whereas the slow KA response was unaffected by Pent in three quarters of the neurons examined. Pent suppressed the Glu response at lower concentrations than required to potentiate responses to gamma-amino butyric acid. Excitatory postsynaptic potentials (EPSPs) elicited by stimulation of mossy fibers were suppressed by Pent. The EPSPs were a little more resistant to Pent than were the Glu responses. These results indicate that Pent blocks receptors for excitatory amino acids in the hippocampus. Of the three different populations of the receptors, Quis receptors are the most sensitive to Pent and KA receptors are the least sensitive. The suppression of the EPSPs is in accordance with the notion that Glu is the transmitter released from mossy fibers.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 23 (1975), S. 293-300 
    ISSN: 1432-1106
    Keywords: Glutamic acid ; Purkinje cell ; Cerebellum ; Brain slice ; Dendrite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribution of glutamate sensitive sites was studied in vitro in thin cerebellar sections from guinea-pigs, in which Purkinje cell bodies and some of the principal dendrites were identified microscopically. Glutamate administered near the cell body induced firing. Stronger excitation, however, was produced when glutamate was administered to the molecular layer along a strip of tissue extending from the soma of the cell under study towards the pial surface of the slice. Excitation induced by glutamate slowly declined in some cells during prolonged administration. D-Glutamate was a weaker excitant than the L-isomer. These results suggest that the dendrite of the Purkinje cell is more sensitive to glutamate than the cell soma.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 37 (1979), S. 387-398 
    ISSN: 1432-1106
    Keywords: Dendritic spike ; Purkinje cell ; Cerebellum ; Calcium spike ; Climbing fibre response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular spikes were recorded simultaneously from dendrites and somata of Purkinje cells in thin cerebellar sections. Spontaneously occurring dendritic spikes were biphasic with the initial phase positive. Triphasic dendritic spikes with a large negative phase appeared during electrophoretic application of glutamate. In media containing procaine, tetrodotoxin, or high concentrations of KCl, negative dendritic spikes occurred whereas soma spikes were abolished. The negative dendritic spikes were suppressed by CoCl2 or MnCl2. Electrical stimulation elicited climbing fibre responses in somata and large negative waves in dendrites. Spikes of dendritic origin were different from those reflecting electrotonic spread of soma spikes. The relation between soma spikes and active dendritic spikes is discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 57 (1985), S. 313-320 
    ISSN: 1432-1106
    Keywords: Excitatory amino acid ; Glutamate ; Aspartate ; Ionic channel ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Properties of excitation induced by various excitatory amino acids were studied in thin slices of the guinea pig hippocampus in the presence of Mn2+, tetrodotoxin and tetraethylammonium chloride. Depolarizations induced by L-glutamate (Glu), quisqualate (Quis) and D-homocysteate (DH) were accompanied consistently by decreases in neuron input resistance. In the current-voltage function, increases in input resistance were never observed at any membrane potential. The amplitude of Glu, Quis and DH responses decreased during tonic outward currents and increased during tonic inward currents. Although neuron input resistance decreased with depolarizations induced by L-aspartate (Asp) as well, the magnitude of the resistance reduction was significantly smaller than that induced by Glu. Asp responses changed in amplitude as did Glu responses during tonic inward and outward currents. Depolarizations induced by N-Methyl-Daspartate (NMDA) were accompanied by apparent increases in input resistance, and their amplitudes increased and decreased during tonic depolarization and hyperpolarization, respectively. Mn2+ was almost without effect at the concentration used (2.7 mM) on responses induced by Glu, DH or Asp. These results suggest that Glu, Quis and DH induce depolarizations in hippocampal neurons by activating only Quis receptors, and that Asp activates Quis receptors preferentially though it activates NMDA receptors as well.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1106
    Keywords: Brain slices ; Ultrastructure ; Synaptic potential ; Metabolism ; Olfactory cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fine structure and electrical activity were studied in thin brain sections prepared from the olfactory cortex of the guinea pig and incubated in vitro in standard and modified conditions. In the standard medium, the potential response was maintained with no marked changes for 4–5 hours and thereafter gradually decreased. The ultrastructure of the tissue was well preserved for the initial 2 hours of incubation. After incubation for 5 hours, many empty spaces were noted. Some dendritic stumps lost fine internal structure, but most of the synapses were apparently normal. Cyanide suppressed the potential response, and caused swelling of the nerve terminals and a decrease in the number of synaptic vesicles. The recovery of the response in the standard medium was not accompanied by a full restoration in the fine structure. If slices were incubated in the absence of glucose and oxygen, with cyanide in glucose-free medium, or at a low temperature, the potential response was irreversibly depressed. In these slices, numerous wide spaces of low electron density were noted which were concluded to have been derived, at least partly, from the swollen dendrites.
    Type of Medium: Electronic Resource
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