Convergence of excitatory and inhibitory hair cell transmitters shapes vestibular afferent responses

doi:10.1073/pnas.0402824101

Convergence of excitatory and inhibitory hair cell transmitters shapes vestibular afferent responses

Departments of ^*Neurology and ^∥Neuroscience, Mount Sinai School of Medicine, New York, NY 10029; ^§Department of Bioengineering, University of Utah, Salt Lake City, UT 84112; ^**National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035; ^††Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110; and ^¶Marine Biological Laboratory, Woods Hole, MA 02543

Edited by Michael V. L. Bennett, Albert Einstein College of Medicine, Bronx, NY (received for review April 22, 2004)

Abstract

The vestibular semicircular canals respond to angular acceleration that is integrated to angular velocity by the biofluid mechanics of the canals and is the primary origin of afferent responses encoding velocity. Surprisingly, some afferents actually report angular acceleration. Our data indicate that hair-cell/afferent synapses introduce a mathematical derivative in these afferents that partially cancels the biomechanical integration and results in discharge rates encoding angular acceleration. We examined the role of convergent synaptic inputs from hair cells to this mathematical differentiation. A significant reduction in the order of the differentiation was observed for low-frequency stimuli after γ-aminobutyric acid type B receptor antagonist administration. Results demonstrate that γ-aminobutyric acid participates in shaping the temporal dynamics of afferent responses.

Footnotes

↵ ‡ To whom correspondence should be addressed. E-mail: gay.holstein{at}mssm.edu.
↵ † G.R.H., R.D.R., and S.M.H. contributed equally to this work.
Author contributions: G.R.H., R.D.R., and S.M.H. designed research; G.R.H., R.D.R., G.P.M., V.L.F., R.D.B., and S.M.H. performed research; G.R.H. and G.P.M. contributed new reagents/analytic tools; G.R.H., R.D.R., G.P.M., V.L.F., R.D.B., and S.M.H. analyzed data; and G.R.H., R.D.R., and S.M.H. wrote the paper.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: GABA, γ-aminobutyric acid; GABA_B, GABA type B; RT, room temperature.