ATP Decreases EPSP Amplitudes in Crayfish Extensor Muscles, while Products of its Hydrolysis Have No Effect

Abstract

Superficial extensor muscles in crayfish tails were exposed to hydrolysable and non-hydrolysable ATP solutions to determine their effects on EPSP amplitudes. A 10mM solution of non-hydrolysable ATP produced a 63% drop in EPSP amplitudes. When hydrolysable ATP was used at the same concentration, a negligible effect was observed. When a tenfold higher concentration of hydrolysable ATP (100mM) was used, we observed similar results as with the nonhydrolysable ATP (a 55% drop). This suggests that the hydrolysis of extracellular ATP reduces its potency and is consistent with the theory that it is only the ATP and not the products of its hydrolysis or the hydrolysis itself that cause the drop in EPSP amplitude.