Voltage- and Patch-Clamp Experiments in Virtual Computer Laboratories (cLABs-Neuron). Hans A. Braun; Horst Schneider; Bastian Wollweber; Heiko B. Braun & Karlheinz Voigt Institute of Physiology, Deutschhausstr. 2, 35037 Marburg, Germany • „cLABs“ is a series of multimedial programs for teaching dynamic biological and physiological mechanisms in an interactive and virtual environment which allows users to perform their own sets of experiments. • cLABs programs are equally suitable for universities and biology classes at schools as well as for private studies. Introduction • “cLABs-Neuron”, our latest cLABs- Software, demon-strates the interrelations between ion channel dynamics and membrane currents and voltages. It consists of the modules: I. Membrane Properties II. Ion Channels III. Voltage-/Current-Clamp Experiments I. Membrane Properties This module provides animations and simulations to basic functions of neuronal membrane properties which are described in terms of their electrical equivalents. Electrical Equivalents Illustrates the functional membrane properties (= bilipid layer and ion channels) and their electrical equivalents (= membrane capacitance and resistance). RC-Circuit Visualises current flows and potential changes across a resistor and a capacitor in a RC-parallel circuit. RC-Lab Allows experiments to examine the voltage changes that occur in a RC-parallel circuit when current pulses are applied and no active elements (e.g. ion channels) are involved. • A variable number of current pulses of pre-selectable amplitude, duration and delay can be applied. • Resistance and capacitance of the RC- circuit can be changed Conductance This interactive section can be used to learn how the membrane potential can be changed with alterations of ionic conductances. For an intuitive understanding we use a simplified circuit which only consider the Na and K currents and even neglect the membrane capacitance (stationary condition). • You can move the sliders of the potentiometers to see how the membrane potential and currents change as a function of the ionic conductances. • The buttons allow pre-sets of the conductances to minimal, maximal or equal values and also simulates the changes during an action potential. Available from: Sheffield BioScience Programs Flat 1 Salisbury Heights 31 Salisbury Road Edinburgh EH16 5AA, UK Tel: + 4 131 662 8225 E-mail: [email protected] Price: €490 £310 (Institutional, multi-user licence) Closing the circuit leads to a constant current flow which divides into a current via the capacitor and the resistor (1-2). At first the major current is flowing on the capacitor. The more the capacitor is charged the more current is flowing through the resistor. When the circuit is opened (3-5), the capacitor discharges across the resistor. (1) (2) (3) (4) (5) (1) (1) Superposition of the potential changes during stimulation with repetitive current pulses. (2) Effect of capacitance changes on the membrane potential after stimulation by a constant current pulse. (2) supported by: BM&T Heidelberg/Marburg DAQ-Solutions, Lohra, TransMIT, Giessen