Sildenafil citrate (VIAGRA)

The new report was published online Aug. 9 and appears in an upcoming issue of the Journal of Physiology. In the study, the scientists measured oxytocin released from rat pituitaries in response to neural stimulation. When the pituitaries were treated with sildenafil, they responded to the stimulation by releasing three times as much oxytocin as they did without the drug. Importantly, the drug had little if any effect on hormone release in the absence of stimulation, Jackson says. “Erectile dysfunction drugs do not induce erections spontaneously, they enhance the response to sexual stimulation,” he 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.”

Though he doesn’t think his findings raise any significant safety issues related to Viagra use, he does think it provides strong rationale for studies of additional effects and new potential uses. “A big question raised by our study is, will sildenafil do the same thing to the nerve terminals that release oxytocin [in the brain]”" he says. The cells that supply oxytocin to the pituitary come from a brain structure called the hypothalamus, which also sends hormones throughout the brain.

Though sildenafil’s effects on these pathways are still unknown, work by other researchers has shown that oxytocin-sensitive cells in the brain play a role in the neural control of erectile responses, suggesting that Viagra and its kin may work through multiple channels.

The famous blue pills could have other uses as well. Oxytocin has been linked to the ability to make strong social bonds, while sildenafil was recently shown to improve hamsters’ abilities to adjust the timing of their internal clocks to overcome simulated jet lag. “This is one piece in a puzzle in which many pieces are still not available,” Jackson says. “But it raises the possibility that erectile dysfunction drugs could be doing more than just affecting erectile dysfunction.”

Researchers at the University of Wisconsin-Madison report this month that sildenafil increases the amount of oxytocin released by stimulation of the posterior pituitary gland, a small structure directly underneath the brain that regulates hormone levels in response to neural signals.

The finding is the first indication of a chemical mechanism through which erectile dysfunction drugs like Viagra may have physical effects besides increasing blood flow to sexual organs, says study author Meyer Jackson, a physiology professor at the UW-Madison School of Medicine and Public Health.

Sometimes called the “love hormone” or “cuddle chemical,” oxytocin 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.

Oxytocin release is regulated by an enzyme that acts like a braking system, limiting hormone release by dampening neural excitation of the cells. This same enzyme, phosphodiesterase type 5, also limits blood flow by contracting the muscles around blood vessels.

In both places, sildenafil works by blocking this enzyme, essentially releasing the brakes, explains Jackson. In blood vessels, relaxing smooth muscle increases blood flow, which corrects erectile dysfunction, and in the posterior pituitary, the cells become more responsive. “The same stimulation will produce more [oxytocin] release.” He says, “I think this is a missing link in terms of trying to sort out the issues around whether there are additional effects of phosphodiesterase type 5 inhibitors,” which include Viagra, Levitra and Cialis.

Testing four plants that are used as natural aphrodisiacs in traditional cultures, a team of Italian researchers has found that the soft green heart-shaped leaf of the horny goat weed may hold the key to a new drug for treating erectile dysfunction.
Mario Dell”Agli, who led the study at the University of Milan, even says that a medication based on horny goat weed may as effective as Viagra, with an additional benefit of lesser side effects.
He has revealed that his team undertook the study to establish the potential of the four plants as alternatives to the famous blue pill.
Viagra’’s active compound, sildenafil, promotes male erection by inhibiting an enzyme called phosphodiesterase-5 (PDE5), which controls blood flow to the penis.
In lab experiments, Dell”Agli and his colleagues tested the four plants to determine their efficacy in inhibiting PDE5.
The researchers observed that just one of the plants Epimedium brevicornum, also known as horny goat weed and Bishop’’s Hat had an effect.
The findings of the study confirm suggestions that a compound found inside the horny goat weed, icariin, is a PDE5 inhibitor.
The research team extracted icariin from the plants, produced six modified versions of it, and tested them on PDE5.
Dell”Agli said that there was one compound that worked as well as Viagra”. He added that a drug made from that compound could also cause fewer side effects than Viagra.
Besides inhibiting PDE5, sildenafil affects other phosphodiesterases that are essential to sight and heart function, and thus people with heart problems are not advised to take the blue pill. Viagra takers often suffer disturbances to their eyesight.
The new compound, however, appears to be safe in terms of such health effects, according to the researchers.
DellAgli reckoned that the compound developed by his team might take about a decade to reach the market, because it has to go through lengthy clinical trials.
“(Meanwhile) if people eat horny goat weed, I think it can be beneficial because it contains icariin. But it will not be as effective as Viagra,” says Dell”Agli.
A research article on the study has been published in the Journal of Natural Products.