Fast Ca2+ Buffer-Dependent Reliable but Plastic Transmission at Small CNS Synapses Revealed by Direct Bouton Recording

Publication date: 19 December 2017
Source:Cell Reports, Volume 21, Issue 12
Author(s): Shin-ya Kawaguchi, Takeshi Sakaba
The small size of presynaptic structures and their rapid function have obscured the mechanisms underlying neurotransmission and plasticity. To dissect the function of conventional small presynaptic boutons, we performed direct recording using axon varicosities of cerebellar granule cells (GCs), a parallel-fiber bouton, in dissociated culture, in which pre- and postsynaptic paired recordings are feasible. Identification and accessibility of EGFP-labeled GC boutons allowed us to patch-clamp record presynaptic voltage-gated Ca²⁺ currents and membrane capacitances, together with excitatory postsynaptic currents. We find that GC boutons have 20 readily releasable vesicles, which are loosely coupled to Ca²⁺ channels and rapidly replenished, and that synaptic strength and short-term plasticity are tightly regulated by intracellular Ca²⁺ buffering. Our functional dissection of small boutons thus reveals the sophisticated design of small synapses capable of reliable but plastic outputs with limited resources.

Graphical abstract

Teaser

Kawaguchi and Sakaba use direct patch-clamp recording from small axonal varicosities to show that granule cell boutons have about 20 rapidly replenishable readily releasable vesicles, which are loosely coupled to Ca²⁺ channels, and that synaptic strength and short-term plasticity are tightly regulated by Ca²⁺ buffering.


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