Reduced endogenous Ca2+ buffering speeds active zone Ca2+ signaling

摘要: Fast synchronous neurotransmitter release at the presynaptic active zone is triggered by local Ca2+ signals, which are confined in their spatiotemporal extent endogenous buffers. However, it remains elusive how rapid and reliable signaling can be sustained during repetitive release. Here, we established quantitative two-photon imaging cerebellar mossy fiber boutons, fire exceptionally high rates. We show that fixed buffers have a surprisingly low Ca2+-binding ratio (∼15) affinity, whereas mobile affinity. Experimentally constrained modeling revealed buffering promotes fast clearance of from firing. Measuring signals different distances zones with ultra-high-resolution confirmed our model predictions. Our results lead to concept reduced enables signaling, suggesting strength limits rate synaptic transmission.