Presynaptic Ca2 channels: A functional patchwork

Abstract

A key step in the release of neurotransmitter is the entry of Ca 2+ into the presynaptic terminal via voltage-activated Ca 2+ channels. N-type and P/Q-type Ca2+ channels play a predominant role but, surprisingly, their distribution across presynaptic terminals lacks any apparent order. They form a patchwork: at some terminals only N-type channels contribute to transmitter release and in others only P/Q-type channels contribute, but in many terminals both sub-types are active. The physiological implications of this non-uniform distribution are starting to emerge. Recent studies reveal that G-protein-mediated depression of N-type channels is stronger than that of P/Q-type channels, whereas vol..