Effects of a nitric oxide synthase Type II inhibitor on compound action potential thresholds in experimental endolymphatic hydrops.
OBJECTIVE
Nitric oxide (NO) is likely to be synthesized by nitric oxide synthase Type II (NOS II) action and may partake in the origin of changes of compound action potential (CAP) threshold observed in guinea pigs with induced endolymphatic hydrops. This study aimed to assess the action of a NOS II inhibitor on CAP thresholds in these experimental samples.


BACKGROUND
In guinea pigs with experimental endolymphatic hydrops, there are lesions on the cochlea and progressive increase of CAP threshold. NOS II was found in the cochlea of this animal model, and it was inferred that NO can contribute by such alterations.


METHODS
The animals were divided into two groups, in which eight received an intake of a NOS II inhibitor, aminoguanidine, and another eight served as a control group. During 16 weeks, CAP thresholds at 1,000, 2,000, 4,000 and 6,000 on electrocochleography were compared between the groups.


RESULTS
The group that had an intake of aminoguanidine showed a lower increase on CAP thresholds at 2,000 (p < 0.05) and 6,000 Hz (p < 0.05) at the 12th postoperative week, and at 1,000 (p < 0.05), 2,000 (p < 0.001), 4,000 (p < 0.001), > and 6,000 Hz (p < 0.001) at the 16th week.


CONCLUSIONS
We conclude that NOS II inhibitor reduced the elevation of CAP thresholds in experimentally induced endolymphatic hydrops.
Ikino
Cláudio Márcio Yudi
CM
Department of Otorhinolaryngology, São Paulo University Medical School, São Paulo, SP, Brazil. claudioikino@hotmail.com
Bittar
Roseli Saraiva Moreira
RS
Sato
Karina Midori
KM
Capella
Newton Macuco
NM
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001300:Audiometry, Evoked Response; D003051:Cochlea / Q000187:drug effects / Q000201:enzymology; D018159:Endolymphatic Hydrops / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology; D005260:Female; D006146:Guanidines / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011897:Random Allocation
D006146:Guanidines; D052247:Nitric Oxide Synthase Type II; C004479:pimagedine