Reduced Mg2+ block of N-methyl-D-aspartate receptor-mediated synaptic potentials in developing visual cortex.
Molecular cloning has demonstrated a diversity of artificially expressed N-methyl-D-aspartate (NMDA) receptors, implying a similar diversity of naturally occurring NMDA receptors in situ. Particularly significant was the success in expression of NMDA receptor classes exhibiting various sensitivities to Mg2+ block, a voltage-dependent channel blockade by Mg2+ that is essential to NMDA receptor functioning. Release from Mg2+ block often allows or facilitates the occurrence of long-term potentiation, a form of synaptic plasticity. Here we show that in the immature visual cortex, which is more susceptible to long-term potentiation than adult visual cortex, synaptically activated NMDA receptors, unlike those in the adult, have varying but clearly reduced sensitivities to Mg2+ block. We propose that the initially expressed, later-eliminated NMDA receptors exhibiting a reduced Mg2+ block may underlie the greater susceptibility to plasticity in the immature neocortex.
Department of Integrative Brain Science, Faculty of Medicine, Kyoto University, Japan.
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Kato
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Yoshimura
D000367:Age Factors; D000818:Animals; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission; D014793:Visual Cortex / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate; D008274:Magnesium