Functional specialization of presynaptic Cav2.3 Ca2+ channels

Ca2+ influx into presynaptic terminals via voltage-dependent Call channels triggers fast neurotransmitter release as well as different forms of synaptic plasticity. Using electrophysiological and genetic techniques we demonstrate that presynaptic Call entry through Ca(v)2.3 subunits contributes to the induction of mossy fiber LTP and posttetanic potentiation by brief trains of presynaptic action potentials while they do not play a role in fast synaptic transmission, paired-pulse facilitation, or frequency facilitation. This functional specialization is most likely achieved by a localization remote from the release machinery and by a Cav2.3 channel-dependent facilitation of presynaptic Call influx. Thus, the presence of Ca(v)2.3 channels boosts the accumulation of presynaptic Ca2+ triggering presynaptic LTP and posttetanic potentiation without affecting the low release probability that is a prerequisite for the enormous plasticity displayed by mossy fiber synapses.