New approaches for analysis of amperometrical recordings

Amperometry is a powerful tool for studying the exocytotic process. Catecholamines released from a single secretory vesicle are oxidized by a carbon fiber microelectrode placed on a chromaffin cell membrane. This phenomenon can be recorded online as an amperometric signal. Each event of exocytosis is called a secretory spike. Several kinetic parameters can be extracted from spikes to get important information about catecholamine storage and to follow the time course of exocytosis. The large amount of data requires the use of computer programs. We describe software, written for Igor Pro (Wavemetrics, Lake Oswego, OR, USA), that allows the offline analysis of amperometric signals. It includes (1) the automatic analysis of a large collection of experiments without user intervention; (2) the visual check of located spikes; (3) data pooling from several experiments to create galleries with hundreds of thousands of spikes. In addition, we have designed a new filtering method for amperometric data. It provides an excellent tool to enhance the signal/noise ratio with minimal artifacts. This filter allows one to obtain more reliable spike parameters.