Objectives: Premature ejaculation is the most common male sexual dysfunction and, yet, no approved effective therapies are currently available. We studied the in vivo effectiveness of hyperforin (HF), a concentrated extract of Hypericum perforatum in an experimental model for the expulsion phase of ejaculation in anesthetized rats.
Methods: The ejaculation model involved inducing rhythmic bulbospongiosus (BS) muscle contractions in male rats under urethane anesthesia (1.2 g/kg subcutaneously) by transiently raising the internal urethral pressure with saline infusion for 2 seconds at a rate of 116 microL/s. Electrodes in the BS muscles recorded the electrical activity during the contractions as a cluster of bursts on the electromyogram. Injection of the 5-hydroxytryptamine type 1A agonist 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) (0.4 mg/kg subcutaneously) intensified the BS muscle contractions induced by increases in urethral pressure.
Results: Administration of 8-OH-DPAT strongly accelerated the ejaculation in the vehicle-treated rats and the amplitude of electrical discharges and the duration of electrical bursts accompanying the increases in urethral pressure were increased from baseline by 203.2% +/- 32.9% and 178.1% +/- 22.9%, respectively. The HF extract reduced the effects of 8-OH-DPAT on ejaculation at lower doses when tested in the dose range of 5 to 80 mg/kg. The reduction in the amplitude of bursts with HF extract remained unchanged after a midthoracic spinal transection, suggesting that the action of HF is either at the spinal ejaculation generator or directly on the neurons innervating the BS muscles.
Conclusions: This is the first report of the effect of HF in a rat model of ejaculation. HF can be considered a novel new treatment of premature ejaculation.