Potentiation of synaptic transmission in the rat hippocampal slice by exogenous L-glutamate and selective L-glutamate receptor subtype agonists.
We have investigated the effects of administration of exogenous glutamate receptor agonists on the amplitude of field excitatory post-synaptic potentials (fEPSPs) evoked in the CA1 region of the rat hippocampal slice by stimulation of the Schaffer collateral-commissural fibres. L-Glutamate applied by iontophoresis or by bath perfusion (50 microM for 5 min) evoked a slowly rising increase in the amplitude of the fESPS which persisted for over 90 min. L-Glutamate induced potentiation was blocked by either D(-)-2-amino-5-phosphonopentanoic acid (40 microM) or by (RS)-alpha-methyl-4-carboxyphenylglycine (500 microM). In slices in which synaptic long-term potentiation had been saturated, iontophoretically applied L-glutamate did not induce further potentiation, but reset the fEPSP amplitude back to control levels. Iontophoretic administration of N-methyl-D-aspartate (NMDA) evoked a transient potentiation which decayed back to control levels within 90 min whereas bath perfusion of NMDA (50 microM) evoked a persistent depression. Bath perfusion of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA, 50 microM) evoked no persistent effects. Bath administration of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD, 50 or 100 microM) caused a short term depression of the fEPSP and no significant persistent effects. Perfusion of 100 microM ACPD in medium containing 1 microM picrotoxin caused a much smaller short term depression of the fEPSP and this was followed by a gradually developing and persistent potentiation.(ABSTRACT TRUNCATED AT 250 WORDS)
Collins
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Department of Biomedical Sciences, University of Aberdeen, Marischal College, U.K.
Davies
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D000818:Animals; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects*; D066298:In Vitro Techniques; D007478:Iontophoresis; D016202:N-Methylaspartate / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects; D009498:Neurotoxins / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D009498:Neurotoxins; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D018698:Glutamic Acid; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid