Neuronal Voltage Gated Potassium Channels May Modulate Nitric Oxide Synthesis in Corpus Cavernosum.

Potassiumchannels (K(+)Ch) in corpus cavernosumplay an important role in the regulation of erection. Nitric oxide (NO) acts through opening of K(+)Ch leading to hyperpolarization and relaxation. Aim : This study aims to update knowledge about the role of voltage-gated K(+)Ch (K-V) channels in erectile machinery and investigate their role in the control of NO action &/or synthesis in the corpus cavernosum. Methods : Tension studies using isolated rabbit corpus cavernosum (CC) strips and rat anococcygeus muscle were conducted. Results are expressed as mean +/- SEM. Results : Electric field stimulation (EFS, 2-16 Hz) evoked frequency-dependent relaxations of the PE (phenylephrine)-precontracted CC strips. At 2 Hz, EFS-induced relaxation amounted to 73.17 +/- 2.55% in presence 4-AP (10(-3) M) compared to 41.98 +/- 1.45% as control. None of the other selective K(+)Ch blockers tested inhibited EFS-induced relaxation. 4-AP (10(-3)M) significantly attenuated ACh-induced relaxation of rabbit CC where dose-response curve was clearly shifted upward, and attenuated SNP-induced relaxation, for example, to 49.28 +/- 4.52% compared to 65.53 +/- 3.01% as control at 10(-6) M SNP. The potentiatory effect of 4-AP on EFS was abolished or reversed in presence of N-G-nitro-L-arginine (L-NNA, non-selective nitric oxide synthase inhibitor, 10(-5)M, and 2 x 10(-4)M). Same results were observed in rat anococcygeus muscle which is a part of the erectile machinery in rats. Conclusion : This study provides evidence for the presence of prejunctional voltage-gated K(+)Ch in CC, the blockade of which may increase the neuronal synthesis of NO.