"Molecular Brain" seminar

Speaker: professor Dmitri Rusakov, Institute of Neurology, University College London (UK)

Presentation title: Activity-dependent remodelling of synaptic microenvironment

Author's abstract:

Memory trace in the brain is believed to involve structural remodelling of synaptic connections. This is likely to engage ultrathin astroglial processes that often occur in the immediate proximity of excitatory synapses. Although astroglia have been emerging as an important regulator of synaptic circuitry, the causal relationships between activity-triggered synaptic restructuring and the changes in nearby astroglia remain poorly understood. We combined single-cell electrophysiology with two-photon excitation microscopy, photolytic uncaging, super-resolution techniques, and correlational 3D electron microscopy, to monitor fine astroglial morphology during the induction of synaptic long-term potentiation (LTP), in situ and in vivo. We document NMDA receptor-dependent withdrawal of astroglial processes from the vicinity of synapses following LTP induction, both at the level of synaptic populations and at the level of individually monitored potentiated synapses. The reduction in synaptic astroglial coverage boosts the extra-synaptic escape of released glutamate thus facilitating NMDA receptor-mediated cross-talk among neighbouring synapses. The cellular mechanisms underlying astroglial restructuring involve local Ca²⁺ elevations but do not depend on metabotropic glutamate receptors, IP₃-receptor signalling, aquaporins, or Ephrin-associated morphogenesis. They do require the ion exchanger NCCK1, thus pointing to the underlying ion and water homeostasis machinery. Experiments are under way to understand activity-dependent changes in the 3D nano-organisation of perisynaptically expressed signalling proteins using dSTORM imaging.

Chair: Alexey Semyanov; E-mail: semyanov@ibch.ru

may 16, 2018

Source: http://conf.molneuro.ru