Micro-injection of trypsin into axons of squid

Abstract

RECENT work appears to show that phospholipids play a fundamental part in membrane physiology1,2. The participation of protein has been thought by some to be more doubtful since external application of proteases seems not to interfere with electrical function of squid, lobster or frog axons 3-5. However, it should be recalled that externally applied protease does produce injury potentials in muscle4. Attempts to demonstrate that protease had entered squid axons without producing changes in electrophysiological properties may have been in error even though the controls at the time seemed appropriate3