Attenuation of Mg2(+)-block of synaptic N-methyl-D-aspartate receptors in the visual cortex of rats raised under optic nerve blockade.
It has been known that the sensitive period for ocular dominance column plasticity is prolonged in animals raised under light deprivation. We tested whether this prolongation is related to a developmental change in Mg2+ block of N-methyl-D-aspartate (NMDA) receptors. Synaptic potentials were recorded intracellularly from visual cortex slices of rats whose optic nerves were blocked bilaterally by tetrodotoxin injected into the eyes for 2-4 weeks of age. In cells from normal rats, the amplitude of NMDA receptor-mediated synaptic potentials became smaller at more negative membrane potentials, and larger at more positive potentials, even at 0.1 mM [Mg2+]o. In cells from tetrodotoxin-treated rats, the voltage-dependence was significantly weaker than in cells from normal rats at 0.1 mM [Mg2+]o. Thus, Mg(2+)-block of synaptic NMDA receptors in the visual cortex may be regulated by optic nerve activity, and may thereby control the sensitivity to synaptic plasticity in an activity-dependent manner.
Department of Integrative Brain Science, Faculty of Medicine, Kyoto University, Japan.
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Yoshimura
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Kato
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D003624:Darkness; D004594:Electrophysiology; D005074:Evoked Potentials, Visual / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008027:Light; D008274:Magnesium / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D009900:Optic Nerve / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D012683:Sensory Deprivation / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D014793:Visual Cortex / Q000737:chemistry* / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D013779:Tetrodotoxin; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D008274:Magnesium