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GABA-mediated giant depolarizing potentials as coincidence detectors for enhancing synaptic efficacy in the developing hippocampus
- *Neuroscience Programme, International School for Advanced Studies, 34014 Trieste, Italy; and †Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Butlerova 5a, 117485 Moscow, Russia
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Edited by Per O. Andersen, University of Oslo, Oslo, Norway, and approved January 14, 2004 (received for review September 16, 2003)
Abstract
Spontaneously occurring neuronal oscillations constitute a hallmark of developmental networks. They have been observed in the retina, neocortex, hippocampus, thalamus, and spinal cord. In the immature hippocampus, the so-called “giant depolarizing potentials” (GDPs) are network-driven synaptic events generated by γ-aminobutyric acid (GABA), which at this stage is depolarizing and excitatory. We have tested the hypothesis that during the first postnatal week, GDP-associated calcium signals may alter the properties of synaptic transmission at poorly developed mossy fiber (MF)-CA3 connections. We found that “pairing” GDPs with MF stimulation induced a persistent increase in synaptic efficacy at MF-CA3 synapses. When the interval between GDPs and MF stimulation was increased, the potentiating effect progressively declined and disappeared. The potentiation depended on activation of voltage-dependent calcium channels and calcium flux. This activity may contribute to the refinement of neuronal connectivity before the establishment of the adult neuronal circuit.
Footnotes
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↵ ‡ To whom correspondence should be addressed. E-mail: cher{at}sissa.it.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: GABA, γ-aminobutyric acid; CPP, α-3-(2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid; CV, coefficient of variation; d-AP5, d-(-)-2-amino-5-phosphonopentanoic acid; DCG-IV, (2S,2′R,3′R)-2-2(2′,3′-dicarboxycyclopropyl) glycine; EPSC, excitatory postsynaptic current; GDPs, giant depolarizing potentials; lAP-4, 2-amino-4-phosphonobutyric acid; LTP, long-term potentiation; MF, mossy fibers; NMDA, N-methyl-d-aspartate; VDCC, voltage-dependent calcium channels; DG, dentate gyrus; BAPTA, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; Pn, postnatal day n.
- Copyright © 2004, The National Academy of Sciences
