Release probability of hippocampal glutamatergic terminals scales with the size of the active zone

Holderith, Noémi and Lőrincz, Andrea and Katona, Gergely and Rózsa, Balázs and Kulik, Ákos and Watanabe, Masahiko and Nusser, Zoltán (2012) Release probability of hippocampal glutamatergic terminals scales with the size of the active zone. NATURE NEUROSCIENCE, 15 (7). pp. 988-997. ISSN 1097-6256 (print); 1546-1726 (online)

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Abstract

Cortical synapses have structural, molecular and functional heterogeneity; our knowledge regarding the relationship between their ultrastructural and functional parameters is still fragmented. Here we asked how the neurotransmitter release probability and presynaptic [Ca2+] transients relate to the ultrastructure of rat hippocampal glutamatergic axon terminals. Two-photon Ca2+ imaging–derived optical quantal analysis and correlated electron microscopic reconstructions revealed a tight correlation between the release probability and the active-zone area. Peak amplitude of [Ca2+] transients in single boutons also positively correlated with the active-zone area. Freeze-fracture immunogold labeling revealed that the voltage-gated calcium channel subunit Cav2.1 and the presynaptic protein Rim1/2 are confined to the active zone and their numbers scale linearly with the active-zone area. Gold particles labeling Cav2.1 were nonrandomly distributed in the active zones. Our results demonstrate that the numbers of several active-zone proteins, including presynaptic calcium channels, as well as the number of docked vesicles and the release probability, scale linearly with the active-zone area.

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