GABA-mediated giant depolarizing potentials as coincidence detectors for enhancing synaptic efficacy in the developing hippocampus.
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 gamma-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.
Kasyanov
Alexander M
AM
Neuroscience Programme, International School for Advanced Studies, 34014 Trieste, Italy.
Safiulina
Victoria F
VF
Voronin
Leon L
LL
Cherubini
Enrico
E
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D006153:Guanosine Diphosphate / Q000378:metabolism; D006624:Hippocampus / Q000254:growth & development / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D013569:Synapses / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D015220:Calcium Channels; D006153:Guanosine Diphosphate; D005680:gamma-Aminobutyric Acid; D002118:Calcium