Presynaptic Ca2+ channels: a functional patchwork.
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 Ca(2+) 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 voltage-dependent relief of inhibition is more pronounced for P/Q-type channels. The patchwork distribution of Ca(2+) channel subtypes might therefore enable terminal-specific modulation of transmitter release, enhancing the power of synaptic processing.
Reid
Christopher A
CA
Department of Physiology, University of Melbourne, Grattan St, 3010, Parkville, Victoria, Australia. careid@unimelb.edu.au
Bekkers
John M
JM
Clements
John D
JD
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D006801:Humans; D009415:Nerve Net / Q000502:physiology*; D017729:Presynaptic Terminals / Q000502:physiology*
D015220:Calcium Channels