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Guest Lynne Clemens

So This Is What Prolactin Does!

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Guest Rose Marie

Report:

Orgasmic endocrinology

Investigator: Tillmann Kr?ger

 

http://news.bmn.com/confere....t&num=4

 

22 June 2003

 

by Bea Perks

 

 

German researchers are on their way to identifying the neuroendocrine response to sexual activity. Their findings could lead to new therapies for sexual dysfunction, and add to the growing body of evidence for a physiological role for orgasm.

 

The methodological approach developed by Tillmann Kr?ger at the University of Essen in Germany and colleagues in Essen and in Sydney, Australia, is straightforward, but the sensitivity of the topic they are studying means that little is known in the field of sexual drive and orgasm.

 

Their approach enables the continuous recording of neuroendocrine response to sexual stimulation. Subjects are required to watch an "emotionally neutral" documentary film for 20 minutes, followed by 20 minutes of an "erotic" film, before a final 20 minutes of documentary. Ten minutes into the erotic film, subjects are asked to masturbate, or have intercourse until orgasm.

 

Throughout this, subjects are continuously monitored by cardiovascular and neuroendocrine parameters. "To ensure the privacy of participants, we established a method of continuous blood withdrawal by a small portable pump," said Kr?ger. Tubes and wires attached to the subject's arm are passed from the isolated test room into an adjacent room where researchers can monitor blood flow and levels of circulating hormones. Blood is withdrawn at about 1-2 ml per minute.

 

The main finding from this series of studies is that plasma prolactin levels are substantially increased following orgasm in both men and women, but unchanged following sexual arousal without orgasm. Prolactin levels remain elevated for an hour of more following orgasm, they report.

 

"The consistent finding of orgasm-induced prolactin release raises the question of biological relevance," said Kr?ger. Elevated levels of prolactin, known as hyperprolactinemia, have consistently been shown to suppress sexual drive and lead to sexual dysfunction in men and women, he says.

 

Hyperprolactinemia commonly occurs during pregnancy and lactation (prolactin helps in the preparation of the breasts for milk production) but is also associated with pathological conditions, in particular a pituitary tumor called a prolactinoma, which secretes high levels of prolactin and can occur in both men and women.

 

But this is distinct from the biological relevance of acute post-orgasmic prolactin release. "First, prolactin may impact upon peripheral reproductive organs - either precipitating mechanisms that are essential for successful fertility, proconception, and pregnancy," said Kr?ger, "and/or prolactin may inhibit further sexual activity," he said. Alternatively, "it may be an endocrine regulator of human sexual behavior," he suggests.

 

Kr?ger has been testing the hypothesis that prolactin forms feedback mechanisms to the central nervous system, where it modifies the activity of dopaminergic neurons in the brain.

 

Due to ethical and practical difficulties, Kr?ger is not able to introduce prolactin or prolactin antagonists into his subjects, "Nevertheless," he said, "we know that manipulation of prolactin release may be conducted at the level of the hypothalamus pituitary."

 

In order to monitor possible neurological effects of prolactin on sexual response, Kr?ger used a system where prolactin levels could be pharmacologically reduced to low physiological levels using a drug called cabergoline, which is normally used to reduce prolactin levels in patients with prolactinoma.

 

Subjects treated in this way then followed the initial protocol designed to monitor sexual response. The resulting data show that subjects with pharmacologically reduced prolactin levels have increased sexual drive or desire compared with untreated controls.

 

Sexual drive and desire were measured on the basis of continuous cardiovascular monitoring and reports from subjects, who were in contact with researchers via an intercom system. There was no difference, however, between controls and subjects with low prolactin levels when it came to orgasm. Both groups achieved orgasm as normal.

 

"Cabergoline is a dopamine agonist," said Kr?ger. "However, it seems that the enhancing effects of decreased prolactin levels on sexual drive and function are not exclusively explainable by the direct dopaminergic effects of cabergoline."

 

Indeed, he discovered that increasing prolactin levels by treating subjects with thyrotropin-releasing hormone (TRH), which simulates the release of prolactin in the pituitary, completely abrogated the sexual increase observed with a single cabergoline administration. "Thus, the dopaminergic properties of cabergoline may regulate the increase in sexual experience, but this is probably somewhat dependent on prolactin levels as well."

 

Although his findings are inconclusive, they point the way to future research. "Prolactin is at least a cheap and reliable marker of orgasm in sex research," concluded Kr?ger. Further, he predicted, "cabergoline is probably a new pharmacological approach for treatment of sexual disorders."

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As Arte Johnson used to say"Vettty intewesting" I wonder what population base they are recruiting their test participants

from-Not that I'd be interested or anything!

Diana

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