Similar intracellular Ca2+ requirements for inactivation and facilitation of voltage-gated Ca2+ channels in a glutamatergic mammalian nerve terminal.

Voltage-gated Ca2+ channels (VGCCs) of the P/Q-type, which are expressed at a majority of mammalian nerve terminals, show two types of Ca2+-dependent feedback regulation-inactivation (CDI) and facilitation (CDF). Because of the nonlinear relationship between Ca2+ influx and transmitter release, CDI and CDF are powerful regulators of synaptic strength. To what extent VGCCs inactivate or facilitate during spike trains depends on the dynamics of free Ca2+ ([Ca2+]i) and the Ca2+ sensitivity of CDI and CDF, which has not been determined in nerve terminals.

The role of physiological afferent nerve activity during in vivo maturation of the calyx of Held synapse.

We studied how afferent nerve activity affects the in vivo maturation of a fast glutamatergic CNS synapse, the calyx of Held. To address this question, we exploited the distinct presynaptic Ca2+ channel subtypes governing transmitter release at the cochlear inner hair cell (IHC)-spiral neuron synaptic junction compared with those at higher synapses along the auditory pathways. We characterized the functional properties of calyx synapses in wild type (wt) compared with those developing in Ca(V)1.