Presynaptic Ca2+ dynamics, Ca2+ buffers and synaptic efficacy.
In synapses neurotransmitter release is triggered by elevation of Ca2+ concentration at a Ca2+ sensor of the release machinery. The Ca2+ concentration at the release site at the given time point is determined by Ca2+ dynamics within presynaptic terminal. It depends on a source of Ca2+ (usually voltage-gated Ca2+ channels), diffusional distance between the source of Ca2+ and the Ca2+ sensor and Ca2+ buffering by endogenous Ca2+ buffers. In many synapses transmitter release can be enhanced (facilitated) during repetitive activity of neurons. The main source of facilitation is activity-dependent increase of Ca2+ concentration at the release site. Several mechanisms of facilitation have been proposed, namely, accumulation of residual Ca2+, multi-site (X receptor) mechanism and partial Ca2+ buffer saturation mechanism. In this review we discuss theoretical and experimental evidence in favor of one or the other of proposed mechanisms.
Burnashev
Nail
N
Department of Experimental Neurophysiology, Faculty of Earth and Life Sciences, CNCR, Vrije Universiteit Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands. nail@bio.vu.nl
Rozov
Andrei
A
D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D006801:Humans; D017729:Presynaptic Terminals / Q000502:physiology*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*
D002021:Buffers; D015220:Calcium Channels; D002118:Calcium