Preliminary Study of Effects of Type V Phosphodiesterase Inhibitor(Vardenafil) on Oxytocin Expression in the Rat Paraventricular Nucleus

Joo, Kwan Joong; Park, Heung Jae; Kim, Khae Hawn

Abstract

PURPOSE: The present study investigated the effects of the type 5 phosphodiesterase(PDE-5) inhibitor, vardenafil on oxytocin expression in the paraventricular nucleus(PVN) of the hypothalamus were investigated.
MATERIALS AND METHODS
Spargue-Dawley rats received a 2-week oral treatment with vardenafil(0.25 mg/kg/day oral adminstration, n=5) or(0.5 mg/kg/day oral adminstration, n=5) or(1 mg/kg/day oral adminstration, n=5) or (2 mg/kg/day oral adminstration, n=5) or control(n=3). Oxytocin expression in the paraventricular nucleus was measured. These experiments were performed in the absence of sexual stimulation for at least 36 hours before the experiments.
RESULTS
The number of oxytocin-positive cells in the PVN was 46.88+/-15.46/section in the control group, 61.42+/-26.37/section in the 0.25 mg/kg vardenafil-treated group, 78.00+/-33.44/section in the 0.5 mg/kg vardenafil-treated group, 78.81+/-37.18/section in the 1 mg/kg vardenafil-treated group and 94.61+/-57.38/section in the 2 mg/kg vardenafil-treated group. The number of oxytocin-positive cells in the PVN increased in a concentration-dependent manner.
CONCLUSIONS
Daily vardenafil administration increases expression of oxytocin in the PVN in a dose-dependent fashion in the absence of sexual stimulation. Thus, these results imply that the PDE-5 inhibitor vardenafil has a direct effect on the erectile pathway in the central nervous system in the absence of sexual stimulation.