CODING MECHANISMS IN VESTIBULAR AFFERENT AXONS

Project Details

Description

A class of large diameter afferent nerve fibers innervate the
otolithic or otoconial organs, the saccule, utricle, and lagena
(of non-mammals) and the three semicircular canal cristae in a
spatially selective manner. Each of these nerve fibers innervate
several sensory hair cells. The physiological response of each
fiber presumably results from combining inputs from all innervated
hair cells, and physiological dogma presumes that each hair cell
that synapses on an afferent fiber has roughly the same potential
for influencing action potential generation of that fiber. By
using a cytochemical cation-binding procedure that identifies the
axonal locations where action potentials may be initiated,
preliminary results suggest that an individual hair cell synapsing
with these large diameter fibers may directly generate a
regenerative potential if the post-synaptic potential produced is
sufficiently large. Synapses of adjacent hair cells do not stain,
suggesting that other pre-synaptic hair cells may not have the same
capacity. Initiation of an action potential at the post-synaptic
membrane would insure orthodromic conduction of hair cell responses
through the intraepithelial internodal segment of the terminal to
the axon proper. This proposal will study the cation binding of post-synaptic
membrane in vestibular end-organs of fish, frogs, birds, and
mammals. The questions to be considered are (1) the spatial
distribution of cation binding post-synaptic membrane; (2) the
phylogenic distribution of cation binding post-synaptic membrane
in the saccule and utricle of the 4 vertebrate groups named
previously; and (3) the relationship between the hair cells
synapsing onto a single branch of an eighth nerve fiber and cation-
binding post-synaptic membrane.
StatusFinished
Effective start/end date12/31/897/31/90

Funding

  • National Institute of Neurological Disorders and Stroke

ASJC

  • Medicine(all)
  • Neuroscience(all)
  • Physiology

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