Release probability of hippocampal glutamatergic terminals scales with the size of the active zone.
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 [Ca(2+)] transients relate to the ultrastructure of rat hippocampal glutamatergic axon terminals. Two-photon Ca(2+) 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 [Ca(2+)] 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.
Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
Noemi
N
Holderith
Andrea
A
Lorincz
Gergely
G
Katona
Balázs
B
Rózsa
Akos
A
Kulik
Masahiko
M
Watanabe
Zoltan
Z
Nusser
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D020864:Calcium Channels, N-Type / Q000378:metabolism / Q000648:ultrastructure; D006624:Hippocampus / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013572:Synaptic Vesicles / Q000378:metabolism*
D020864:Calcium Channels, N-Type