An ultracompliant glass microelectrode for intracellular recording.

We describe the simple fabrication of a glass microelectrode that was designed for the stable impalement of contracting isolated cardiac preparations. The electrodes can be made with the aid of a standard pipette puller. The design uses a long-shanked glass electrode that is stepped below the shoulder at 70 degrees to the shaft and again near the tip. The electrodes are of marginally higher resistance than equivalent length straight electrodes (34.9 vs. 26.0 M omega). The stepped design imparts a low stiffness to the electrode in the vertical and horizontal planes, and the mechanical basis for this performance is described and discussed with regard to measured behavior. The duration of impalements with stepped electrodes is significantly longer than for straight electrodes and can usually be maintained for indefinite periods with minimal damage to small, highly contractile muscle preparations.