An iconographic program for computer-controlled whole-cell voltage clamp experiments.
A Macintosh-based system is described for performing instrument control, data acquisition and storage operations in single-electrode whole-cell voltage clamp experiments. The system consists of a commercially available voltage clamp amplifier, multifunction input/output (I/O) board, graphical programming language (LabVIEW 2) and custom built 'virtual instrument' (VI). The I/O board is capable of fast (up to 110 ksample/s) multichannel analog-to-digital (A/D) conversion with 12-bit resolution. It can control the gain settings of the clamp unit through digital I/O lines and generate the P/N leak subtraction protocol to eliminate the linear portion of capacitive currents using analog output voltages and gating pulses. Complete voltage clamp protocols can be implemented using the on-screen front panel controls of the VI. It enables the user to visualize the acquired data, to graph sets of current-voltage (I-V) relations or to fit single-exponential functions to one current trace. To evaluate the adequacy of whole-cell recording, the total membrane capacitance (Cm), the series resistance (Rs) and the time constant (tau c) of the decay of the capacitive current are calculated using the single-exponential function fit to the data. The system is particularly well suited to the study of large quantities of transmembrane I-V relationships. Source code for the crucial elements of the VI as well as sample recordings from a cultured spinal cord neuron, illustrating system operation, are presented.
Budai
D
D
Department of Pharmacology, University of Minnesota, Medical School, Minneapolis 55455.
Kehl
L J
LJ
Poliac
G I
GI
Wilcox
G L
GL
D000669:Amplifiers, Electronic; D000818:Animals; D002478:Cells, Cultured; D003196:Computer Graphics; D004594:Electrophysiology / Q000295:instrumentation*; D015640:Ion Channel Gating; D007473:Ion Channels; D008838:Microcomputers; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology
D007473:Ion Channels