ABSTRACT
Conventional equipment for recording of membrane potentials in research laboratories includes a microelectrode, headstage, micromanipulator, amplifier, oscilloscope, a timing device and usually a loudspeaker system. Current-clamp mode is usually chosen for direct measurement of membrane potential. In this mode the experimenter can inject steady-state current into a neuron to change membrane potential. Many ionic channels of the neuronal membrane are voltage-dependent, i.e. the conductance of the channels varies as membrane potential changes. Historically, voltage-clamp experiments were undertaken using two intracellular electrodes, one measuring membrane potential and the second measuring membrane current. Membrane potential is measured at the tip of the sharp microelectrode and compared with the value that the experimenter ‘commands’. The difference between measured membrane potential and the command potential is obtained and current sufficient to force membrane potential to equal the command potential is passed via a microelectrode into the neuron.
