Studying electric field effects on embryonic myocytes.

Several problems arise when electrophysiological measurements are attempted on cells exposed to an electric field. In addition to field distortion produced by the reference electrode, membrane potential measurements by conventional microelectrode or patch-clamp techniques suffer serious interference from the applied field. We describe here a novel method for measurement of cardiac myocyte response to an alternating electric field that avoids these problems by sensing the mechanical activity of the cells rather than their electrical activity. A miniature electromechanical force transducer is used for this purpose. A glass pipet is attached to the force transducer, and only this pipet makes actual contact with the cell preparation. The resistive elements of the transducer are arranged as two legs of a Wheatstone bridge. Contractile activity of the cells produces small displacements of the micropipet and a resulting change in the transducer resistances. The Wheatstone bridge output is a current signal that is detected and converted to a voltage signal by a picoammeter before amplification and recording for later analysis. The technique may find applications in a variety of experimental studies of contractile tissues.