Nitric oxide in glutamate-induced compound action potential threshold shifts.
OBJECTIVE
Investigate the role of NO as a neurotransmitter in the gerbil cochlea and the effects of (7-NI) on compound action potential (CAP) threshold elevations induced by l-glutamate, an agonist at the NMDA glutamate receptor subtype, to further elucidate the role of NO in cochlear excitotoxicity.


METHODS
In anesthetized gerbils, CAP thresholds were recorded before and after cochlear perfusions with a control solution of artificial perilymph (APS) and a test solution of L-glutamate (GA) in three experimental groups.


RESULTS
The control group showed no CAP threshold elevations (p<0.05) when APS was perfused after systemic pre-treatment with 7-NI. GA perfusion alone caused significant elevation (p<0.05) of the mean cochlear CAP threshold (25 dB SPL+/-5.8 dB to 78 dB SPL+/-19.5 dB). The CAP threshold elevation was prevented (p<0.05) when the animals were pretreated with 7-NI before GA perfusion (24 dB SPL+/-4.2dB to 27 dB SPL+/-6.7 dB).


CONCLUSIONS
NO mediates excitotoxicity when the cochlea is perfused with L-glutamate.
Patel
Mihir R
MR
Department of Otolaryngology, Head and Neck Surgery, Bioinformatics Building CB# 7070, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7070, USA.
Stamat
Jocelyn C
JC
Zdanski
Carlton J
CJ
Ebert
Charles S
CS
Prazma
Jiri
J
D000200:Action Potentials; D000818:Animals; D003055:Cochlear Microphonic Potentials; D004305:Dose-Response Relationship, Drug; D005849:Gerbillinae; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D007191:Indazoles / Q000494:pharmacology; D008954:Models, Biological; D016202:N-Methylaspartate / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010477:Perfusion; D017470:Receptors, Glutamate / Q000378:metabolism; D013997:Time Factors
D007191:Indazoles; D018377:Neurotransmitter Agents; D017470:Receptors, Glutamate; D009569:Nitric Oxide; D018698:Glutamic Acid; D016202:N-Methylaspartate; C080122:7-nitroindazole