Organelle movement in axons depends on ATP

Abstract

When living axons are examined in the light microscope many of the membrane-bounded organelles they contain can be seen to undergo rapid saltatory movements, predominantly in the retrograde direction¹. This is thought to be an important component in the fast transport of materials in axons, the mechanism of which is unknown although cytoskeletal elements such as actin filaments and microtubules are probably involved (see ref. 2 for review and refs). I describe here experiments in which giant axons from the legs of the crab Carcinus maenas have been made permeable to ions and small molecules using a high voltage discharge to puncture holes in the plasma membrane³. This allows, in a suitable buffer, movement to be arrested due to the loss of metabolites and then reactivated by the addition of exogenous ATP, thus showing directly for the first time that rapid saltatory motion in axons is an ATP-requiring process.