Intracavernosal pressure with cavernosal nerve stimulation after long-term administration of GB0710. After administration of GB0710 at doses of 20, 40, 100 and 150 mg, intracavernosal pressure increased in a dose- and duration-dependent fashion. *P<0.05, the difference between treatment and control by Mann–Whitney U test; †P<0.05, the difference among various groups at the same concentrations of each treatment by Kruskal–Wallis test.