ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of salvia miltiorrhiza injection (SM) on gentamicin (GM)-induced expression of nitric oxide synthase (NOS) isoforms in guinea pig cochlea, and to explore the protective mechanism of SM on GM-induced ototoxicity.</p><p><b>METHODS</b>40 guinea pigs were randomly assigned to 4 groups: control group, GM group, SM group and GM plus SM group. Expression of NOS isoforms in the guinea pig cochlea was detected by the SABC method of immunohistochemistry and microscope image analysis technique. Auditory threshold was tested by auditory brainstem response (ABR) measurement.</p><p><b>RESULTS</b>Inducible NOS (iNOS/NOS II) expression and ABR threshold in GM plus SM group were both significantly declined as compared with those in GM group (P < 0.01). Moreover, change of iNOS expression was in high correlation with that of ABR threshold ([r] > 0.7, P < 0.01). While expression of neuronal NOS (nNOS/NOS I) and endothelial NOS (eNOS / NOS III) showed no significant differences in all groups.</p><p><b>CONCLUSION</b>SM had no effect on the expression of nNOS and eNOS, but could inhibit iNOS high-expression induced by GM to reduce excessive generation of NO, therefore SM could protect against GM ototoxicity.</p>