Stéphane Pagès

EMAIL:

POSITION:

Postdoctoral fellow

ACADEMIA:

Ph.D. - Physical Chemistry, Université de Genève (http://www.unige.ch)

M.Sc. - Physical Chemistry, Université de Bordeaux 1 (http://www.u-bordeaux1.fr)

ADVISORS:

Daniel Côté (http://dcclab.ca)

Paul De Koninck (http://www.greenspine.ca)

RESEARCH INTERESTS:

Voltage and calcium imaging, synaptic plasticity

Research Summary

Dendritic spines are known to play a key role in synaptic transmission and plasticity. In the synapse, the information travelling from one neuron to the other is encoded into postsynaptic membrane potential (Vm) transients. The knowledge of the exact nature of these local Vm transients is therefore crucial for understanding synaptic transmission and plasticity. Optical techniques based on the use of voltage-sensitive dye (VSD) are known for a long time to be able to report membrane potentials. However, due to their low sensitivity and to the extremely small size of a spine, local detection in a synapse is very challenging. In our lab, we use the water soluble voltage-sensitive dye ANNINE6-plus to image Vm in dendritic spines (Figure 1).

Figure 1: Staining and imaging ANNINE6-plus voltage sensitive dye in cultured hyppocampal neurons. A) Fluorescence signal from one photon excitation of the dye at 458 nm. B) One hour after the initial staining, there is no internalization of the dye allowing to perform experiments over long periods of time. Scale bar represents 10 microns.

The extracellular staining of cultured hippocampal neurons is highly efficient and the sensitivity of the dye to membrane depolarization Delta F/F is amongst the larger ever reported (> 10 % /100 mV). Moreover the submillisecond time response of the dye allows for detection of action potentials. In addition, the high signal over noise ratio (S/N) of measurements is sufficient to record a somatic action potentials in a single trial while only 10 averages are required to report a damped action potential invading a dendritic spine (Figure 2).

Figure 2: Optical monitoring of back propagating action potentials invading a dendritic spine. A) Cultured hippocampal neuron expressing cytosolic Cerulean as a morphological dye and stained with ANNINE6-plus. Scale bar is 10 microns. B) Top - two action potentials induced by induced by injection of 2 ms 1 nA currents. Bottom - optical recording of the the subsequent back propagated action potentials in the spine. The red trace is the ANNINE6-plus fluorescence time profile whereas the blue one is for Cerulean. 10 traces were average.

Publications

Nicolet O, Banerji N, Pagès S, Vauthey E. Effect of the excitation wavelength on the ultrafast charge recombination dynamics of donor-acceptor complexes in polar solvents. (http://www.ncbi.nlm.nih.gov/pubmed/16834210) J Phys Chem A. 2005 Sep 22;109(37):8236-45.

Pagès S, Lang B, Vauthey E. Ultrafast excited state dynamics of the perylene radical cation generated upon bimolecular photoinduced electron transfer reaction. (http://www.ncbi.nlm.nih.gov/pubmed/16774195) J Phys Chem A. 2006 Jun 22;110(24):7547-53

Macpherson BP, Bernhardt PV, Hauser A, Pagès S, Vauthey E. Time-resolved spectroscopy of the metal-to-metal charge transfer excited state in dinuclear cyano-bridged mixed-valence complexes. (http://www.ncbi.nlm.nih.gov/pubmed/16022552) Inorg Chem. 2005 Jul 25;44(15):5530-6.

Fedunov RG, Feskov SV, Ivanov AI, Nicolet O, Pagès S, Vauthey E. Effect of the excitation pulse carrier frequency on the ultrafast charge recombination dynamics of donor-acceptor complexes: Stochastic simulations and experiments. (http://www.ncbi.nlm.nih.gov/pubmed/15303931) J Chem Phys. 2004 Aug 22;121(8):3643-56.