Volume 17, Number 19,
Issue of October 1, 1997
pp. 7523-7531
Copyright ©1997 Society for Neuroscience
The Glutamate Receptor Subunit
1 Is Highly Expressed in Hair
Cells of the Auditory and Vestibular Systems
Received June 25, 1997; accepted July 21, 1997.
Saaid Safieddine and
Robert J. Wenthold
Laboratory of Neurochemistry, National Institute on Deafness and
Other Communication Disorders, National Institutes of Health, Bethesda,
Maryland 20892
In the inner ear, fast excitatory synaptic transmission is mediated
by ionotropic glutamate receptors, including AMPA, kainate, and NMDA
receptors. The recently identified
1 and
2 glutamate receptors
share low homology with the other three types, and no clear response or
ligand binding has been obtained from cells transfected with
alone
or in combination with other ionotropic receptors. Studies of mice
lacking expression of
2 show that this subunit plays a crucial role
in plasticity of cerebellar glutamatergic synapses. In addition, these
mice show a deficit in vestibular compensation. These findings and the
nature of glutamatergic synapses between vestibulocochlear hair cells
and primary afferent dendrites suggest that
receptors may be
functionally important in the inner ear and prompted us to investigate
the expression of
receptors in the cochlea and peripheral
vestibular system. Reverse transcription and DNA amplification by PCR
combined with immunocytochemistry and in situ
hybridization were used. Our results show that the expression of
1
in the organ of Corti is intense and restricted to the inner hair
cells, whereas
1 is expressed in all spiral ganglion neurons as well
as in their satellite glial cells. In the vestibular end organ,
1
was highly expressed in both hair cell types and also was expressed in
the vestibular ganglion neurons. The prominent expression of
1 in
inner hair cells and in type I and type II vestibular hair cells
suggests a functional role in hair cell neurotransmission.
Key words:
cochlea;
vestibular end organ;
hair cells;
spiral
ganglion neurons;
PCR;
in situ hybridization;
Western
blot;
immunocytochemistry