Viagra Also Enhances 'Feel-Good' Hormone

A U.S. study found a chemical mechanism through which erectile dysfunction drugs may have physical effects besides increasing blood flow to sexual organs.

Researchers at the University of Wisconsin-Madison, led by Meyer Jackson, report that the drug sildenafil -- sold as Viagra -- increases the amount of oxytocin, which plays several important roles in social interactions and reproduction, including triggering uterine contractions and lactation. It is also released during orgasm and has been linked to sexual arousal, says Jackson.

An enzyme that acts like a braking system limits the release of oxytocin by dampening neural excitation of the cells. Sildenafil works by blocking this enzyme, essentially releasing the brakes, explains Jackson.

Erectile dysfunction drugs do not induce erections spontaneously, they enhance the response to sexual stimulation, Jackson says. The same thing is happening in the posterior pituitary -- Viagra will not induce the release of oxytocin on its own, but it will enhance the amount of release you get in response to electrical stimulation.

The findings are published in the Journal of Physiology.

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