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Séminaire - Haruyuki Kamiya Physiology of single CNS axon: rediscovery of analog tuning of axonal spikes.

Abstract :

Conférence d'Haruyuki Kamiya dans le cadre d’un contrat CNRS/JSPS

 Axons are the sole output of the neurons which carry neuronal information to the presynaptic terminals with highly reliable digital processes.

However, the reliability of spike propagation along single axons and its use-dependent modulation or refractoriness by preceding neural activity remains mostly untested in the mammalian CNS. We recently have established direct recording from the single axon terminals of hippocampal mossy fibers. Taking advantage of reasonable size of the axon terminals, the button-like structures were visualized clearly with IR-DIC optics in unstained slices. This allows direct recordings of spikes from single axon terminals with high temporal resolution and high signal to noise ratio without averaging. In response to paired stimuli at short intervals, the amplitude of action potentials was slightly, but reproducibly decreased in comparison with the first responses. This small reduction of the axonal spikes might affect the amount of presynaptic calcium entry and therefore could be the critical determinants of the synaptic strength. To address how preceding axonal spikes affect subsequent responses, the results of pharmacological experiments using modulators of sodium channels as well as the results of realistic numerical simulation will be discussed.

Selected publications

Ohura S, Kamiya H: Excitability tuning of axons in the central nervous system. J. Physiol. Sci., in press

ŸKamiya H: Photocamical inactivation analysis of temporal dynamics of postsynaptic native AMPA receptors in hippocampal slices. J. Neurosci., 32: 6517-6524, 2012

 Shimizu H, Fukaya M, Yamasaki M, Watanabe M, Manabe T, Kamiya H: Use-dependent amplification of presynaptic Ca2+ signaling by axonal ryanodine receptors at the hippocampal mossy fiber synapse. Proc. Natl. Acad. Sci. USA 105, 11998-12003, 2008

ŸKamiya H, Ozawa S, Manabe T: Kainate receptor-dependent short-term plasticity of presynaptic Ca2+ influx at the hippocampal mossy fiber synapses. J. Neurosci., 22: 9237-9243, 2002

ŸKamiya H, Ozawa S: Kainate receptor-mediated presynaptic inhibition at the hippocampal mossy fibre synapse. J. Physiol. (Lond.), 523: 663-665, 2000