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  • Hippocampus  (4)
  • Cyclic AMP  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Testing of prototype antiepileptics in hippocampal slices (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 332 (1986), S. 89-92 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Hippocampus ; Antiepileptics ; Penicillin ; Low Ca2+
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects of six prototype anticonvulsant drugs, phenytoin, carbamazepine, midazolam, phenobarbital, ethosuximide and sodium valproate, were evaluated in two different experimental models of epileptiform activity using the in vitro slice preparation from the rat hippocampus. The relative potencies of the agents were determined: a) in the complete absence of synaptic transmission by recording spontaneous burst firing from the CA 1 pyramidal cell layer in a low calcium high magnesium solution and b) during blocked synaptic inhibition by observing the activity of each drug upon orthodromically evoked population spikes in penicillin containing medium. The rank order of potencies was a) in low Ca2+: carbamazepine, phenytoin, midazolam, phenobarbital, valproate, ethosuximide; b) in penicillin containing medium: midazolam, phenobarbital, carbamazepine, phenytoin, valproate, ethosuximide. These observations illustrate that the use of multiple paradigms is warranted when examining the mechanisms of action of new anticonvulsants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00633203
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  • 2
    Digitale Medien
    Digitale Medien
    Patch clamp study of histamine activated potassium currents on rabbit olfactory bulb neurons (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 386-393 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Brain slice ; Patch-clamp ; Rabbit ; Cyclic AMP ; Potassium current ; Histamine receptors Olfactory bulb
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Effects of histamine, histamine agonists and antagonists on steady state current in principal neurons and interneurons were investigated in thin slices from the olfactory bulb of newborn rabbits with the nystatin perforated patch-clamp technique and local pipette application. No change in steady state current was observed in mitral cells. In most of the periglomerular, juxtaglomerular and granular cells, however, H1-receptor activation caused an outward current; a similar effect, but mostly not on the same neurons was elicited by 8-bromo-cyclic-AMP. These currents were reversed at the potassium equilibrium potential and blocked by apamin and therefore probably represent calcium sensitive potassium currents. H2-receptor activation caused an inward current which also reversed at the potassium equilibrium potential, indicating block of a potassium current. Specific H3-receptor activation and cyclic GMP were ineffective. Histamine usually caused a combined effect beginning with an inward current. Histaminergic neurons fire with changes in behavioural state and can, by the described mechanisms, markedly influence signal processing in the olfactory bulb.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00172775
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  • 3
    Digitale Medien
    Digitale Medien
    Patch clamp study of histamine activated potassium currents on rabbit olfactory bulb neurons (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 386-393 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Key words Brain slice ; Patch-clamp ; Rabbit ; Cyclic AMP ; Potassium current ; Histamine receptors ; Olfactory bulb
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Effects of histamine, histamine agonists and antagonists on steady state current in principal neurons and interneurons were investigated in thin slices from the olfactory bulb of newborn rabbits with the nystatin perforated patch-clamp technique and local pipette application. No change in steady state current was observed in mitral cells. In most of the periglomerular, juxtaglomerular and granular cells, however, H1-receptor activation caused an outward current; a similar effect, but mostly not on the same neurons was elicited by 8-bromo-cyclic-AMP. These currents were reversed at the potassium equilibrium potential and blocked by apamin and therefore probably represent calcium sensitive potassium currents. H2-receptor activation caused an inward current which also reversed at the potassium equilibrium potential, indicating block of a potassium current. Specific H3-receptor activation and cyclic GMP were ineffective. Histamine usually caused a combined effect beginning with an inward current. Histaminergic neurons fire with changes in behavioural state and can, by the described mechanisms, markedly influence signal processing in the olfactory bulb.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00172775
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of histamine on hippocampal pyramidal cells of the rat in vitro (1986)
    Springer
    Experimental brain research 62 (1986), S. 123-130 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Histamine ; H2-receptor ; Hippocampus ; Calcium dependent potassium current
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The actions of bath applied histamine on CA1 pyramidal cells were investigated in hippocampal slices of the rat. Histamine caused a) a slight depolarization but no significant change in resting membrane conductance; b) an abbreviation of long afterhyperpolarizations after single action potentials, bursts of action potentials or TTX resistant spikes; c) a loss of accommodation of firing. In the presence of TEA or barium, histamine prolonged and increased the size and number of the slow TTX resistant spikes. A depolarizing plateau which follows such spikes was also increased by histamine. Evoked synaptic potentials were unaffected by histamine, but the population spike was increased. The frequency of spontaneous chloride dependent potentials, which reflect interneurone firing, was also increased. These effects considerably outlasted histamine application and were mimicked by the H2-agonist impromidine but not the H1-agonist thiazolethylamine, and blocked by the H2-antagonists cimetidine and metiamide but not the H1-antagonists mepyramine or the beta-antagonist propranolol. It is concluded that histamine, by activating H2-receptors, antagonizes a calcium mediated potassium conductance in hippocampal pyramidal cells without affecting calcium current. By this mechanism histaminergic afferent fibres could effectively regulate cortical responsiveness by selectively potentiating large excitatory inputs of target neurones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00237408
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  • 5
    Digitale Medien
    Digitale Medien
    Modulation of low calcium induced field bursts in the hippocampus by monoamines and cholinomimetics (1984)
    Springer
    Pflügers Archiv 400 (1984), S. 28-33 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Hippocampal slice ; Low Ca field bursts ; Monoamines ; Cyclic AMP ; Cholinomimetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The influence of monoamine transmitter candidates, acetylcholine and related substances on rhythmic depolarization shifts (field bursts) in the CA1 area of hippocampal slices from rats in low calcium (0.2 mmol·l−1) high magnesium (4 mmol·l−1) was investigated. Acetylcholine (ACh), histamine (HA) and H2-agonists, noradrenaline (NA) and beta-agonists at nano- to micromolar concentrations as well as dopamine (DA) and 8-bromo-cyclic AMP at 100 μmol·l−1 accelerated the field bursts. H2-antagonists blocked HA actions, beta-antagonists blocked NA actions selectively; muscarinic antagonists blocked ACh, HA and NA actions. H1-agonists, serotonin, dopamine and adenosine slowed the field bursts at micromolar concentrations. These effects parallel the action of the tested substances on afterhyperpolarizations in CA 1 pyramidal cells. High sensitivity and specificity make this response of the field bursts an excellent model to study postsynaptic transmitter actions in the central nervous system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00670532
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  • 6
    Digitale Medien
    Digitale Medien
    Effects of diazepines and barbiturates on hippocampal recurrent inhibition (1977)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 299 (1977), S. 211-218 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Diazepines ; Barbiturates ; Hippocampus ; Recurrent inhibition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects of two diazepines (diazepam and Ro 11-7800) and 3 barbiturates (thiamylal, pentobarbital and phenobarbital) on GABA-mediated recurrent inhibition were assessed on single hippocampal pyramidal cells and on population spikes using extracellular recording techniques. Recurrent inhibition was evoked in spontaneously active CAl pyramidal cells by stimulation of the fimbria or the alveus with single shocks. Microiontophoretic application of Ro 11-7800 or systemic application of diazepines or barbiturates resulted in an increase of the duration of the inhibition and in a concomitant depression of the spontaneous firing in most neurones tested. When the firing rates were kept constant artificially, using excitant amino acids, a prolongation of the recurrent inhibition was observed with barbiturates but not with diazepines. The duration of the inhibition, which was assessed from CAl population spikes elicited by double shocks to the fimbria, was prolonged following systemic application of diazepines or barbiturates. It is concluded that both diazepines and barbiturates are able to potentiate GABAergic recurrent inhibition in the hippocampus. The demonstration of this effect appears to depend critically on certain experimental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00500313
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  • 7
    Digitale Medien
    Digitale Medien
    Action of anticonvulsants on hippocampal slices in Mg-free medium (1989)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 339 (1989), S. 613-616 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Epilepsy ; Hippocampus ; NMDA receptor ; Anticonvulsants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The effects of six prototype anticonvulsant drugs were investigated on epileptiform field potential discharges evoked in hippocampal slices of rats by removing magnesium ions from the perfusion fluid in order to reveal a possible interaction with N-methyl-d-aspartate (NMDA) receptor activation. All drugs reduced the multiple discharges with the following order of potency: midazolam 〉 carbamazepine = phenytoin = phenobarbital 〉 ethosuximide = valproate. They had a stronger depressant effect on the later population spikes but none of them abolished the epileptiform discharge. These effects can be explained by known mechanisms of action of the anticonvulsants tested and lend no support for a specific interaction with NMDA receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00168652
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