AbstractMale penis is required to become erect during copulation. In the upper (dorsal) part of penis, the erectile tissue termed corpus cavernosum (CC) plays fundamental roles for erection by regulating the inner blood flow. When blood flows into the CC, the microvascular complex termed sinusoidal space is reported to expand during erection. A novel in vitro explant system to analyze the dynamic erectile responses during contraction/relaxation is established. The current data show regulatory contraction/relaxation processes induced by phenylephrine (PE) and nitric oxide (NO) donor mimicking dynamic erectile responses by in vitro CC explants. Two-photon excitation microscopy (TPEM) observation shows the synchronous movement of sinusoidal space and the entire CC. By taking advantages of the CC explant system, tadalafil (Cialis) was shown to increase sinusoidal relaxation. Histopathological changes have been generally reported associating with erection in several pathological conditions. Various stressed statuses have been suggested to occur in the erectile responses by previous studies. The current CC explant model enables to analyze such conditions through directly manipulating CC in the repeated contraction/relaxation processes. Expression of oxidative stress marker and contraction-related genes, Hypoxia-inducible factor 1-alpha (Hif1a), glutathione peroxidase 1 (Gpx1), Ras homolog family member A (RhoA), and Rho-associated protein kinase (Rock), was significantly increased in such repeated contraction/relaxation. Altogether, it is suggested that the system is valuable for analyzing structural changes and physiological responses to several regulators in the field of penile medicine.