Vacuum erection device (VED),used to treat radical prostatectomy (RP)-associated erectile dysfunction,has attracted considerable attention.However,the optimal negative pressure remains to be determined.This investigation explored the optimal pressure for VED therapy in penile rehabilitation.Thirty-six 9-week-old male rats were randomly divided into six groups:control groups (sham group,bilateral cavernous nerve crush [BCNC] group) and VED therapy groups (-200 mmHg group,-300 mmHg group,-400 mmHg group,-500 mmHg group).BCNC group and VED therapy groups underwent BCNC surgery.Intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio was calculated to assess erectile function.Masson\'s trichrome (MT) staining,terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay,immunohistochemistry,and real-time polymerase chain reaction (RT-PCR) were performed to explore cellular and molecular changes of the penis.Compared to the BCNC group,ICP/MAP ratios in all VED treatment groups were improved significantly (all P ＜ 0.05),but there were no statistically significant differences among VED therapy groups.With increased pressure,complications gradually emerged and increased in frequency.Expression of molecular indicators,such as endothelial nitric oxide synthase (eNOS) and alpha-smooth muscle actin (α-SMA),increased after VED therapy,and hypoxia-inducible factor 1α (HIF-1α) and transforming growth factor beta (TGF-β) decreased.In addition,VED therapy improved the outcomes of MT and TUNEL assay.This investigation demonstrated a pressure of-200 mmHg in a rat model is optimal for VED therapy for penile rehabilitation after RP.No further benefits were observed with increased pressure,despite an increase in complications.