Enhancement of Neurotransmitter Release by Activation of Ryanodine Receptors after Ca2+-Dependent Priming at Motor Nerve Terminals

Abstract

Ryanodine receptors at frog motor nerve terminals need priming by repetitive Ca2+entry before activation by further Ca2+entry. Ryanodine receptors were primed by Ca2+entry at a rate of >2 Hz at the external Ca2+concentration > 0.05 mM, while their activation required Ca2+entry at a rate of >20 Hz. Ca2+-induced Ca2+release via ryanodine receptors thus primed and activated markedly augmented impulse-induced release of transmitter from frog motor nerve terminals over several tens of minutes.