Oxygen / Collagen Connection - Physiology of Erectile Dysfunction

[Hawk]

Below is some interesting information on penile health and collagen that I have never seen connected quite this way before.  This could possibly explain increased incidence of Peyronies Disease after prostatectomy, catheterization, and aging in general, not to mention the suggested impact from smoking.  It could also explain any positive results from heat which increases blood flow. Since this is a partial reference, I also provided the link at the end so those interested can view the original document in full for as long as the link remains operational.

ANATOMY AND PATHOPHYSIOLOGY
The penis is composed of the corpus Cavernosum, two spongy columns of erectile tissue, and the corpus spongiosum which is also composed of erectile tissue and contains the urethra, the tube that carries urine from the body.  Erectile tissue is rich in tiny pool-shaped blood vessels called cavernous sinuses, which are surrounded by smooth muscles and supported by elastic fibrous tissue composed of collagen. In the flaccid or unerect state of the normal penis, the small arteries leading to the cavernous sinuses contract, reducing the inflow of blood. The smooth muscles of the tiny blood vessels within the penis are also contracted, and the blood they contain leaks out of the surrounding spongy tissue. When a man becomes aroused, his central nervous system stimulates the release of a number of chemicals, including acetylcholine and nitrous oxide, that relax the smooth muscles in the penis, allowing blood to flow into the tiny
pool-like sinuses and flood the penis. The spongy chambers almost double in size due to the increase in blood flow. The veins surrounding the corpus cavernosum and corpus spongiosum are squeezed almost completely shut by the pressure of the erectile tissue and in turn are unable to drain blood causing the penis to become rigid.

Oxygen from the blood has an important role in erectile health. Oxygen levels vary widely from reduced levels in the flaccid state to very high levels in the erect state. During sleep, oxygen levels are high and a man can normally have three to five nocturnal erections per night, each lasting from 20 to 40 minutes. These nocturnal erections are thought to be part of the body's natural maintenance of healthy erectile tissue. Oxygen levels appear to affect two substances that are important in achieving erection: transforming growth factor 1 (TGF-B1) and prostaglandin E1.

The smooth muscles in the penis produce TGF-B1, a component of the immune system, and one of its roles is to produce collagen. Collagen contributes not only to structural tissue in the body, but is also the material that comprises scar tissue. Prostaglandin E1, among its other functions, opens blood vessels and suppresses collagen production. There is some evidence that when oxygen levels become too low, TGF-B1 production increases and prostaglandin production decreases. If oxygen levels become too low, smooth muscles atrophy and collagen is overproduced, causing scarring and loss of elasticity and reduced blood flow to the penis. Infrequent erections deprive the penis of oxygen-rich blood. Without daily erections, collagen production increases and eventually may form a tough tissue that interferes with blood flow in the penis.[/b][/u]The penis is enervated by two sets of nerves: autonomic (sympathetic and arasympathetic) and somatic (sensory and motor). From the neurons in the spinal cord and peripheral ganglia, the sympathetic and parasympathetic nerves merge to form the cavernous nerves, which enter the corpus cavernosum to effect the neurovascular events during erection and detumescence (subsidence of the erect penis). The somatic nerves are primarily responsible for sensation of the penis and the contraction of the bulbocavernous and ischiocavernous muscles which play a major role in the development of an erection.
The parasympathetic nerve fibers to the penis arise from neurons associated with the second, third, and fourth sacral spinal cord segments. These fibers interact with nerve fibers enervating the rectum, bladder, and prostate. The sympathetic nerves originate from the eleventh thoracic to the second lumbar spinal segments. Stimulation of the parasympathetic nerves induces erection, whereas stimulation of the sympathetic nerves causes detumescence. Damage to the autonomic pathways enervating the penis may eliminate the ability to achieve a psychogenic erection initiated by the central nervous system. Spinal cord lesions may produce varying degrees of erectile dysfunction depending on the location and completeness of the lesions.

Sensory receptors in the penile skin, glans, urethra, and within the corpus cavernosum respond to touch/stimulation and send messages via the nerve tracts to the spinal cord and eventually to the thalamus and sensory cortex in the brain. Tactile stimulation of the external genitalia produces a reflexogenic penile erection in normal men and also in men with supra-sacral spinal cord lesions.

Studies in primates and rodents have identified the medial preoptic area (MPOA) of the brain as an important integration center for sexual drive and psychogenic penile erection. Electrical stimulation of this area in animals produces erection. Pathologic processes in these region, such as Parkinson's disease, stroke or severe head trauma, are often associated with impotence. A variety of neurotransmitters, including dopamine, norepinephrine, and serotonin, have been identified in the MPOA. It appears that dopaminergic and adrenergic receptors may promote, and serotonin receptors inhibit, sexual drive and erectile function.

In summary, the previously mentioned structures and pathways are responsible for the three types of erection: psychogenic, reflexogenic, and nocturnal. Reflexogenic erection is provided by tactile stimuli to the genitalia. This type of erection is preserved in patients with an upper spinal cord injury. Psychogenic erection originates from audio-visual stimuli or fantasy where signals descend from the brain to the spinal erection center to activate the erectile process. This type is preserved in only a small percentage of patients with a complete sacral cord lesion. Nocturnal erections occur mostly during REM sleep, by some unknown mechanism, with impulses traveling from the brain to the spinal cord to induce penile erection.

Author: Steven A. Scott, Pharm.D.
Associate Professor of Clinical Pharmacy
School of Pharmacy and Pharmacal Sciences
Purdue University

http://72.14.207.104/search?q=cache:ZbXciNt3hSIJ:www.continuingeducation.com/pharmacy/impotencetreatment/impotencetreatment.pdf+erection+%2Btrazadone+%2BPathophysiology&hl=en&client=firefox-a