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The correlated blanching of synaptic bodies and reduction in afferent firing rates caused by transmitter-depleting agents in the frog semicircular canalSynaptic bodies (SBs) associated with rings of synaptic vesicles and well-defined, pre- and post-synaptic membrane structures are indicators of maturity in most hair cell-afferent nerve junctions. The role of the SBs remains elusive despite several experiments showing that they may be involved in storage of neurotransmitter. Our results demonstrate that SBs of the adult posterior semicircular canal (SCC) cristae hair cells become less electron dense following incubation of the SCC with the transmitter-depleting drug tetrabenazine (TBZ). Objective quantification and comparison of the densities of the SBs in untreated and TBZ-treated frog SCC demonstrated that TBZ significantly decreased the electron density of SBs. This reduction in electron density was accompanied by a reduction in firing rates of afferent fibers innervating the posterior SCC. A second transmitter-depleting drug, guanethidine, previously shown to reduce the electron density of hair cell SBs, also reduced the firing rates of afferent fibers innervating the posterior SCC. In contrast, the electron density of dense granules (DG), similar in size and shape to synaptic bodies (SB) in hair cells, did not change after incubation in TBZ, thus indicating that granules and SBs are not similar in regard to their electron density. The role of SBs in synaptic transmission and the transmitter, if any, stored in the SBs remain unknown. Nonetheless, the association of the lessening of electron density with a reduction in afferent firing rate provides impetus for the further investigation of the SB's role in neurotransmission.
Document ID
20050000495
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Guth, P.
(Tulane University School of Medicine New Orleans, LA 70112-2699)
Norris, C.
Fermin, C. D.
Pantoja, M.
Date Acquired
August 22, 2013
Publication Date
April 1, 1993
Publication Information
Publication: Hearing research
Volume: 66
Issue: 2
ISSN: 0378-5955
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: DC00303
CONTRACT_GRANT: DC00712
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Neuroscience
NASA Program Space Biology
NASA Discipline Number 40-10
Non-NASA Center

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