title: Developmental refinement of vesicle cycling at Schaffer collateral synapses.
abstract: At synapses formed between dissociated neurons, about half of all synaptic vesicles are refractory to evoked release, forming the so-called "resting pool." Here, we use optical measurements of vesicular pH to study developmental changes in pool partitioning and vesicle cycling in cultured hippocampal slices. Two-photon imaging of a genetically encoded two-color release sensor (ratio-sypHy) allowed us to perform calibrated measurements at individual Schaffer collateral boutons. Mature boutons released a large fraction of their vesicles during simulated place field activity, and vesicle retrieval rates were 7-fold higher compared to immature boutons. Saturating stimulation mobilized essentially all vesicles at mature synapses. Resting pool formation and a concomitant reduction in evoked release was induced by chronic depolarization but not by acute inhibition of the protein phosphatase calcineurin. We conclude that synapses in CA1 undergo a prominent refinement of vesicle use during early postnatal development that is not recapitulated in dissociated neuronal culture.
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. trose@neuro.mpg.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Rose
authors.forename: Philipp
authors.initials: P
authors.lastname: Schoenenberger
authors.forename: Karel
authors.initials: K
authors.lastname: Jezek
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Oertner
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D056547:CA1 Region, Hippocampal / Q000254:growth & development* / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology*; D013572:Synaptic Vesicles / Q000502:physiology*