REGENERATION OF PARTICULAR SYNAPSES

Project: Research project

Project Details

Description

Individual neurons in the leech can regenerate severed axons to
reconnect with particular neurons that are their normal synaptic
targets. In many animal species injured adult neurons may at first
glance seem to revert to their developmental state, but there can
be important differences between adult repair and embryonic
development, including differences in synaptic function. Taking
advantage of identifiable cells and cell types in the leech, the
proposed project addresses the questions: (1) is axon sprouting
controlled by certain cells and cellular interactions, (2) are
particular molecules such as leech "laminin" and surface markers
on mechanosensory neurons associated with directed growth and
repair, (3) do microglia play a critical role in regeneration, (4)
can protein synthesis and transport in short axon systems,
particularly during regeneration, be studied by injection of
synthetic mRNA's, (5) how does cell structure determine synaptic
function and connectivity, and (6) do mechanisms that produce
successful repair recapitulate those that guide embryonic
development? The methodology will include electrophysiological
recording and intracellular injection of markers for subsequent
light and electron microscopic examination. Growing axons and
migrating cells labelled with fluorescent markers will be tracked
in living preparations with the aid of low-light video enhancement.
Properties of pathways and surfaces of particular cells that bind
cell-specific ligands including monoclonal antibodies will be
examined with electron microscopy. Identified neurons and axons
will be injected with mRNA synthesized in vitro that codes for
cytoplasmic and integral membrane proteins. Single cells will be
killed with intracellular injection of proteases or focally
lesioned with an argon laser and fluorescent dyes. The morphology
of certain cells and the complex patterns of normal and regenerated
synaptic contacts between them will be reconstructed with a
computer. Growth of individual cells will be studied during
development and compared with regeneration. Understanding
mechanisms for development and accurate regeneration in the leech
central nervous system might suggest ways that nerve regeneration
in higher animals including humans could be made more reliable and
precise.
StatusFinished
Effective start/end date12/31/897/31/91

Funding

  • National Institute of Neurological Disorders and Stroke
  • National Institute of Neurological Disorders and Stroke
  • National Institute of Neurological Disorders and Stroke
  • National Institute of Neurological Disorders and Stroke
  • National Institute of Neurological Disorders and Stroke

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