Electrophysiology using LabVIEW-RT

[Steve.J]

Dynamic clamping is a method of studying the ion channels in nerve cells and other cells with excitable membranes.  When these channels open, sodium, potassium and other ions are allowed to migrate into/out-of the cell causing a net current flow and a voltage across membrane.  Studying the modulation of these ion channels is an important tool for better understanding these cells and for exploring the behavior of drugs on these cells.

The technique depends on creating a seal between a glass micropipette and the cell membrane with the goal of capturing only one or two ion channels under the seal at the micropipette tip (the tip opening is tiny - only about 1um diameter).  The micropipette is then filled with an ionic solution and a thin recording wire is inserted.  Special amplifiers are used to either control the current through the membrane while measuring voltage, or alternatively hold the voltage constant and measure the current that flows when the channels open/close.  Either way, the membrane conductance can be monitored and directly correlated to the opening/closing of the ion channels.

G-clamp is an application developed by Dr. Paul Kullman while at the University of Pittsburgh School of Medicine to implement a dynamic clamp using LabVIEW Real-time and National Instruments I/O in concert with standard microelectrode amplifiers. Unlike the analog control systems used in typical patch-clamp amplifiers, this system uses a digital high-speed control system running under LabVIEW-RT to implement dynamic current or voltage clamping at 40khz or faster - plenty fast enough to obtain high fidelity recordings of nerve action potentials and ion channel currents.  Since the control system is all done in LabVIEW it is fully customizable - a true "virtual instrument" for electrophysiology.

Full documentation and source code is available at http://hornlab.neurobio.pitt.edu/