(1) Block of conduction and marked increase in permeability of the squid giant axon, when surrounded by adhering small nerve fibers, is caused by the venoms of cottonmouth, ringhals, and cobra snakes and by phospholipase A (PhA). This phenomenon is associated with a marked breakdown of the substructure of the Schwann sheath into masses of cytoplasmic globules. Low concentrations of these agents...
