A simple hanging-drop patch-clamp technique for studying single channel activities in excised membrane patches

A simple hanging-drop technique has been developed for examining the effects of reagents available in limited quantities such as some proteolytic enzymes and site-directed antibodies on single sodium channel activities in patches excised from hippocampal neuronal membranes. The advantages of the technique are as follows: 1. a very small volume (2–4 l of the buffer solution containing the agents to be tested; 2. recording under static conditions without using continuous perfusion systems; 3. reduced background current noise. The use of the technique for studying modifications of single channel parameters under the influence of agents available in limited amounts is illustrated by modification of single sodium channels by treatment with papain.