[Experimental study on the effect of nitric oxide on cochleas of guinea pigs]

The effects of nitric oxide (NO), 1-monoarginine (L-Arg), sodium nitroprusside (SNP) and N-methyl-1-monoarginine (NMLA) (which is an antagonist of nitric oxide synthase) on endocochlear potential, compound action potential(CAP) and cochlear microphonic(CM) of cochleas were studied by means of perilymphatic perfusion of the agents. The results showed that NMLA reduced EP, CAP and CM, L-Arg perilymphatic perfusion could reverse the change caused by NMLA. Continuous NO perilymphatic release restored the changes of EP, CAP and CM back to normal, sometimes above normal, followed by rapid reduction. After SNP perilymphatic perfusion, EP, CAP and CM went up transiently and then declined gradually and remained at a lower level. Addition of NMLA did not reverse the changes. The change of the latent period of CAP N1 and drift of CM was consistent with their amplitude changes. It was suggested that NO might help maintaining inner ear function under physiological condition and participate in controlling the micromechanical character and sensitivity of cochlear hair cells, undue expression of NO may cause toxicity to cochleas.