title: Presynaptic activation of silent synapses and growth of new synapses contribute to intermediate and long-term facilitation in Aplysia.
abstract: The time course and functional significance of the structural changes associated with long-term facilitation of Aplysia sensory to motor neuron synaptic connections in culture were examined by time-lapse confocal imaging of individual sensory neuron varicosities labeled with three different fluorescent markers: the whole-cell marker Alexa-594 and two presynaptic marker proteins-synaptophysin-eGFP to monitor changes in synaptic vesicle distribution and synapto-PHluorin to monitor active transmitter release sites. Repeated pulses of serotonin induce two temporally, morphologically, and molecularly distinct presynaptic changes: (1) a rapid activation of silent presynaptic terminals by filling of preexisting empty varicosities with synaptic vesicles, which parallels intermediate-term facilitation, is completed within 3-6 hr and requires translation but not transcription and (2) a slower generation of new functional varicosities which occurs between 12-18 hr and requires transcription and translation. Enrichment of empty varicosities with synaptophysin accounts for 32% of the newly activated synapses at 24 hr, whereas newly formed varicosities account for 68%.
authors.affiliation: Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA.
authors.forename: Joung-Hun
authors.initials: JH
authors.lastname: Kim
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Udo
authors.forename: Hsiu-Ling
authors.initials: HL
authors.lastname: Li
authors.forename: Trisha Y
authors.initials: TY
authors.lastname: Youn
authors.forename: Mary
authors.initials: M
authors.lastname: Chen
authors.forename: Eric R
authors.initials: ER
authors.lastname: Kandel
authors.forename: Craig H
authors.initials: CH
authors.lastname: Bailey
mesh_terms: D000818:Animals; D001048:Aplysia / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism / Q000502:physiology