The Journal of Neuroscience, September 15, 2001, 21(18):7428-7437
Correlation of AMPA Receptor Subunit Composition with Synaptic
Input in the Mammalian Cochlear Nuclei
Stephanie M.
Gardner1,
Laurence O.
Trussell2, and
Donata
Oertel1
1 Department of Physiology, University of Wisconsin
Medical School-Madison, Madison, Wisconsin 53706, and
2 Oregon Hearing Research Center, Vollum Institute, Oregon
Health and Science University, Portland, Oregon 97201
The composition of AMPA receptors in patches excised from somata
and dendrites of six cell types in the mammalian cochlear nuclei was
probed and compared electrophysiologically and pharmacologically with
the rapid application of glutamate. Cells excited predominantly by
auditory nerve fibers had AMPA receptors with exceptionally rapid
gating (submillisecond deactivation and desensitization time
constants). The nonlinear current-voltage relationship in the presence
of spermine showed that few of these receptors had GluR2 subunits, and
the insensitivity of desensitization to cyclothiazide indicated that
they contained mostly flop splice variants. At synapses made by
parallel fibers, AMPA receptors were slowly gating (time constants of
deactivation and desensitization >1 msec) and contained higher levels
of GluR2 and flip isoforms. However, receptors at auditory nerve
synapses on cells that also receive parallel fiber input, the fusiform
cells, had intermediate properties with respect to kinetics and
contained GluR2 and flip isoforms. Given the diverse biophysical
properties, patterns of innervation, patterns of electrical activity,
and targets of each cell type in vivo, these data
indicate that the kinetics and permeation properties of AMPA receptors
are linked to factors associated with synaptic connectivity.
Key words:
AMPA receptor; auditory pathways; GluR2; polyamine; rectification; kinetics; flop; cochlear nuclei; cyclothiazide; deactivation; desensitization; targeting
Copyright © 2001 Society for Neuroscience 0270-6474/01/21187428-10$05.00/0
