Membrane properties of Aplysia neurones intracellularly injected with phospholipases A and C

Publisher Website
Google Scholar
Abstract
The effects of phosholipases A from bee venom and from porcine pancreas and of phospholipases C from Clostridium welchii [C. perfringens] and Bacillus cereus on active and passive membrane properties of Aplysia neurons were studied. Consistent alterations in electrical membrane properties followed intracellular application of 3 of these enzymes. Bee venom phospholipase A produced a rapid decrease of membrane potential and resistance. Voltage clamping revealed a marked depression of peak transient current with little or no effect in the late outward current. Mammalian phospholipase A was ineffective in changing either the resting or active membrane properties. Phospholipase C from B. cereus led to a strong hyperpolarization and a fall in membrane resistance. Voltage clamping revealed a marked increase in the late outward current. Neurons injected with C. welchii phospholipase C manifested a several-fold rise in resting membrane resistance and a tendency to slight hyperpolarization. All enzymes were ineffective when externally applied. The internally applied phospholipases probably affect specific ionic permeabilities in the resting and active excitable membrane. Various mechanisms by which the differing actions of enzymes of the same type could be explained are discussed.