[Role of nitric oxide in the corpus cavernosum reactions evoked by hydrogen peroxide].

Corpus cavernosum smooth muscle spends the majority of its time in the contracted state consisting of tonic and tetanic components. Tetanic component is a result of superposition of phasic contrations ocuring spontaneously with a frequency of 5-27/minute. Hydrogen peroxide (H2O2) in concentration of 10(-3) mol/l causes a transient increase in tetanic contraction lasting 5 to 8 minutes, followed by either recovery of spontaneous activity or inhibition of its frequency and muscle strip relaxation. 30 minutes pretreatment with the specific blocker of NO syntase, L-NAME, does not affect the intrinsic spontaneous activity parameters but enhances H2O2 evoked reaction, increasing both the amplitude and duration of the transient contraction by 41.2 +/- 14.5 and 52.5% +/- 22.8% (n=9) correspondingly. By contrast, the exogenous NO donors nitroglycerin and sodium nitroprusside, cause spontaneous activity inhibition and muscle strip relaxation resulting in the decrease of H2O2 evoked contraction and duration by 8.7 +/- 3.7 and 24.5% +/- 10.6% (n=7) correspondingly. These results suggest that tetanic contraction is an important component of corpus cavernosum smooth muscle tone which is modulated by free radical oxygen species and controlled by NO dependent mechanism.