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Phentolamine relaxes human corpus cavernosum by a nonadrenergic mechanism activating ATP-sensitive K+ channel

International Journal of Impotence Research volume 17, pages 27–32 (2005)Cite this article

Abstract

To investigate the pharmacodynamics of phentolamine in human corpus cavernosum (HCC) with special attention to the role of the K+ channels. Strips of HCC precontracted with nonadrenergic stimuli and kept in isometric organ bath immersed in a modified Krebs–Henseleit solution enriched with guanethidine and indomethacine were used in order to study the mechanism of the phentolamine-induced relaxation. Phentolamine caused relaxation (≈50%) in HCC strips precontracted with K+ 40 mM. This effect was not blocked by tetrodotoxin (1 μM) (54.6±4.6 vs 48.9±6.4%) or (atropine (10 μM) (52.7±6.5 vs 58.6±5.6%). However, this relaxation was significantly attenuated by L-NAME (100 μM) (59.7±5.8 vs 27.8±7.1%; P<0.05; n=8) and ODQ (100 μM) (62.7±5.1 vs 26.8±3.9%; P<0.05; n=8). Charybdotoxin and apamin (KCa-channel blockers) did not affect the phentolamine relaxations (54.6±4.6 vs 59.3±5.2%). Glibenclamide (100 μM), an inhibitor of KATP-channel, caused a significant inhibition (56.7±6.3 vs 11.3±2.3%; P<0.05; n=8) of the phentolamine-induced relaxation. In addition, the association of glibenclamide and L-NAME almost abolished the phentolamine-mediated relaxation (54.6±5.6 vs 5.7±1.4%; P<0.05; n=8). The results suggest that phentolamine relaxes HCC by a nonadrenergic–noncholinergic mechanism dependent on nitric oxide synthase activity and activation of KATP-channel.

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Authors and Affiliations

  1. Surgery Department, Federal University of Ceara, Fortaleza, Ceara, Brazil

    L F G Silva, M E Moraes, P R L Vasconcelos & M O Moraes

  2. Veterinary College, State University of Ceara, Fortaleza, Ceara, Brazil

    N R F Nascimento & M C Fonteles

  3. Department of Pharmacology, UNICAMP, Campinas, Brazil

    G de Nucci

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  1. L F G Silva
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  2. N R F Nascimento
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  3. M C Fonteles
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Correspondence to L F G Silva.

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Silva, L., Nascimento, N., Fonteles, M. et al. Phentolamine relaxes human corpus cavernosum by a nonadrenergic mechanism activating ATP-sensitive K+ channel. Int J Impot Res 17, 27–32 (2005). https://doi.org/10.1038/sj.ijir.3901269

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