Composition of the excitatory postsynaptic potentials recorded from rat visual cortical neurons in layer. II/III: An in vitro electrophysiological and pharmacological studies.
Intracellular recordings were performed on layer II/III neurons of rat brain slices. Neuronal responses to electrical stimulation of the white matter was analyzed pharmacologically using D-2-amino-5-phosphonovalerate (APV), a specific antagonist of the N-methyl-D-aspartate (NMDA) receptor, and kynurenate (Kyn), a broad-spectrum antagonist of both the NMDA and the non-NMDA (kainate and quisqualate) receptors. Fifty-five neurons produced an excitatory postsynaptic potential (EPSP) in response to a single shock. In forty-eight neurons (87%) of them, the EPSP consisted of an APV-sensitive component and an APV-insensitive component. While in seven neurons (13%), it consisted of only the APV-insensitive component. The APV-sensitive component was preceded by the APV-insensitive component and was enhanced in amplitude and duration by the following procedures: a) applying repetitive stimulations to the white matter, b) reducing Mg2+ concentration in the bathing solution and c) depolarizing cell membrane. The APV-insensitive component was affected by neither repetitive stimulation nor reduction of Mg2+ concentration. Both APV-sensitive and APV-insensitive components were reduced by the treatment of Kyn. These suggest that in bathing medium containing Mg2+, the APV-sensitive (i.e. the NMDA receptor-mediated) EPSP is generated by the non-NMDA receptor-mediated depolarization, which removes the Mg2+ blockade in NMDA receptor-gated channel.
Laboratory of Neuroinformation Science, Faculty of Liberal Arts, Tohoku Gakuin University, Sendai, Japan.
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Takahashi
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Ogawa
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D007736:Kynurenic Acid / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*
D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter