Androgenic Maintenance of Inflow and Veno-Occlusion during Erection in the Rat

Abstract

Ongoing studies in this laboratory are designed to determine the role of androgens in the maintenance of the erectile response in the rat. Testosterone-treated castrated rats (TESTO) and untreated castrated rats (CASTRATE) were used for measurement of the rate at which blood flows into the cavernous sinuses by timed collections of blood after partial amputation of the penis. A laser Doppler flow meter was employed to determine whether androgens also regulate the veno-occlusive mechanism that controls the rate of blood flow out of the sinuses. Erection was induced by direct electrical stimulation of the autonomic ganglion that controls cavernosal blood flow in the erectile response. The results of these studies showed that blood flow into the sinuses was approximately twice as great in the TESTO animals as the CASTRATE rats. Furthermore, during ganglionic stimulation, veno-occlusion occurred in the TESTO rats but failed to occur in the CASTRATE rats. The dependence of these responses on nitric oxide (NO) was demonstrated by showing that injection of sodium nitroprusside (SNP) enhances the intracavernosal pressure response in TESTO rats but not CASTRATE animals. However, when SNP injection was combined with ganglionic stimulation, veno-occlusion did occur in the CASTRATE animals. Taken together, these studies show that both the rate of blood flow into the cavernous sinuses and the blood flow out are under androgenic regulation and may involve the actions of NO.

The relationship between hypogonadism and erectile dysfunction

“…22 Noradrenaline is one of the putative vasoconstrictors of penile arterioles and sinusoids that help maintain the penis in a flaccid state. In an animal study, Mills et al 22 proposed that androgens are critical for maintaining erectile function by supporting the responsiveness of vascular smooth muscle to vasoactive drugs.…”

“…22 Noradrenaline is one of the putative vasoconstrictors of penile arterioles and sinusoids that help maintain the penis in a flaccid state. In an animal study, Mills et al 22 proposed that androgens are critical for maintaining erectile function by supporting the responsiveness of vascular smooth muscle to vasoactive drugs. In addition to these trophic effects through transcriptional regulation, androgens may also regulate vascular smooth muscle contractility by nongenomic mechanisms, such as relaxation of coronary arteries by activating potassium channels and inhibiting calcium channels.…”

“…T may also contribute to the penile venous occlusion mechanism that maintains erections. 22 The veno-occlusive mechanism depends on the integrity of neural, vascular and endocrine systems, as well as on the fibroelastic properties of the cavernosal tissue. In summary, an androgen deficiency produces reductions in trabecular smooth muscle content and fibroelastic properties, and increased deposition of extracellular matrix, resulting in the accumulation of hollow cells in the subtunical region of the corpus cavernosum.…”

The effects of testosterone deficiency on the structural integrity of the penile dorsal nerve in the rat

“…In the rat model, castration has been shown to result in a significant reduction in intracavernosal pressure, indicating decreased erectile function. [2][3][4][5] When androgen replacement is administered, erectile function is restored. 4,6 Armagan et al 4 proposed that erectile function declines below 10% of the normal physiological plasma testosterone concentration in a dose-dependent fashion.…”

Intracavernosal pressure characteristics analyzed by power spectral density for identifying the phase of penile erection

“…12,13 Furthermore, some urological researches are designed to determine the role of testosterone and nitric oxide in the maintenance of the erectile response in rats. 9,14 Such investigations require an index that reflects the erectile state. For this reason, precise identification of the erection phases in animal models can be used to investigate erectile physiology during different erection phases and to ensure that experimental procedures (for example, drawing blood or applying electrical neurostimulation) are applied during the correct experimental periods.…”