Referenced in: none

Automatically associated channels: Slo1

Title: A generalised method to estimate the kinetics of fast Ca(2+) currents from Ca(2+) imaging experiments.

Authors: Karima Ait Ouares, Nadia Jaafari, Marco Canepari

Journal, date & volume: J. Neurosci. Methods, 2016 Aug 1 , 268, 66-77

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/27163479

Abstract
Fast Ca(2+) imaging using low-affinity fluorescent indicators allows tracking Ca(2+) neuronal influx at high temporal resolution. In some systems, where the Ca(2+)-bound indicator is linear with Ca(2+) entering the cell, the Ca(2+) current has same kinetics of the fluorescence time derivative. In other systems, like cerebellar Purkinje neuron dendrites, the time derivative strategy fails since fluorescence kinetics is affected by Ca(2+) binding proteins sequestering Ca(2+) from the indicator.Our novel method estimates the kinetics of the Ca(2+) current in cells where the time course of fluorescence is not linear with Ca(2+) influx. The method is based on a two-buffer and two-indicator model, with three free parameters, where Ca(2+) sequestration from the indicator is mimicked by Ca(2+)-binding to the slower buffer. We developed a semi-automatic protocol to optimise the free parameters and the kinetics of the input current to match the experimental fluorescence change with the simulated curve of the Ca(2+)-bound indicator.We show that the optimised input current is a good estimate of the real Ca(2+) current by validating the method both using computer simulations and data from real neurons. We report the first estimates of Ca(2+) currents associated with climbing fibre excitatory postsynaptic potentials in Purkinje neurons.The present method extends the possibility of studying Ca(2+) currents in systems where the existing time derivative approach fails.The information available from our technique allows investigating the physiological behaviour of Ca(2+) channels under all possible conditions.