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Sami Boudkkazi"Release-dependent and release-independent variations in synaptic latency"

Abstract :

In the cortex, synaptic latencies display small variations (~1-2 ms) that are generally considered to be negligible.
First, we show that the synaptic latency at monosynaptically connected pairs of L5 and CA3 pyramidal neurons is determined by the presynaptic release probability (Pr): synaptic latency being inversely correlated with the amplitude of the postsynaptic currentand sensitive to manipulations of Pr. Changes in synaptic latency were also observed when Pr was physiologically regulatedin short- and long-term synaptic plasticity. Paired-pulse depression and facilitation were respectively associated with increased and decreased synaptic latencies. Similarly, latencies were prolonged following induction of presynaptic LTD and reduced after LTP induction. We show using the dynamic-clamp technique that the observed co-variation in latency and synaptic strength is a synergistic combination that significantly affects postsynaptic spiking. In conclusion, amplitude-related variation in latency represents a putative code forshort-and long-term synaptic dynamics in cortical networks. Second, it is well know that AP waveform (i.e.amplitude and duration) is dynamically regulated during specific contexts (postnatal development, repetitive activity etc.). By layer 5 pyramidal neurons pairs and simultaneous soma/axon recordings, we show that AP waveform controls synaptic latency. This supposes that ion channels (Nav and Kv) implicated in axonal AP waveform control the latency of the synaptic events in the cortex. The control of synaptic latency results for regulation of presynaptic calcium current in synaptic boutons. In conclusion, whole results show that 2 mechanisms control synaptic latency in the cortex.

Selected publications

Boudkkazi S, Carlier E, Ankri N, Caillard O, Giraud P, Fronzaroli-Molinieres L, Debanne D.
Release-dependent variations in synaptic latency: a putative code for short- and long-term synaptic dynamics.
Neuron. 2007 Dec 20;56(6):1048-60.

Carlier E, Sourdet V, Boudkkazi S, Déglise P, Ankri N, Fronzaroli-Molinieres L, Debanne D.
Metabotropic glutamate receptor subtype 1 regulates sodium currents in rat neocortical pyramidal neurons.
J Physiol. 2006 Nov 15;577(Pt 1):141-54. Epub 2006 Aug 24.

Andreas Frick