Nitric oxide. The chemical doesn't sound particularly sexy, but it plays a singular role in triggering male erections, a fact that's been known for 20 years. But figuring out how to treat erectile dysfunction and help men maintain erections has been far trickier to nail down.

That may be changing, thanks to recent research from John Hopkins Medicine. Researchers have discovered the biochemical process necessary to stay erect, a discovery that may lead to new treatments for erectile dysfunction, an issue that affects 15 to 25 perfect of 65-year-old men long-term, according to WebMD.

In a study of mice, researchers "found a complex positive feedback loop in the penile nerves that triggers waves of nitric oxide to keep the penis erect," a release stated. After the initial release of nitric oxide, the nerve impulses that begin in the brain or from physical stimulation are sustained, thanks to a biochemical process called phosphorylation. This process ensures that nitric oxide continues to be released, maintaining the erections of both mice and men.

And just what exactly does nitric oxide do? Blood vessels use the chemical as a signal to surrounding muscles to relax, which increases blood flow -- a necessity for staying erect.

Now that researchers have found this biochemical loop, new treatments targeting phosphorylation can help "intervene earlier in the arousal process than current medicines approved to treat erectile dysfunction," the release stated. One treatment researchers are looking into is an herbal compound named forskolin, which can keep nitric oxide pumping.

The search for an erectile dysfunction panacea has been on for years, with other researchers targeting nitric oxide as well.

"Age-associated erectile dysfunction involves a decrease in nitric oxide availability and impaired relaxation," wrote scientists who found a potential treatment for erectile dysfunction in spider venom, a toxin that boosts available nitric oxide.

What are some of the other natural treatment for ED used over the years? Take a look at our slideshow.

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  • Arginine

    Nitric oxide is a key component in developing and maintaining an erection. <a href="">The amino acid L-arginine</a> -- found naturally in red meat, fish and wheat germ among other foods -- is known to boost the body's production of nitric oxide and has been used to successful treat ED in the past, according to WebMD. The Natural Medicines Comprehensive Database has also said the <a href="">amino acid could be used to treat ED</a>, Everyday Health reports.

  • Spider Venom

    The toxin PnTx2-6 -- found in the <a href="">venom of the Brazilian wandering spider</a> -- was found to improve "erectile function in aged rats," according to a study published in August.

  • Pomegranate Juice

    Pomegranate juice has a number of health benefits; researchers recently found the tart drink was responsible for l<a href="">owering blood pressure</a>. A 2007 small-scale study that found promising results in using <a href="">pomegranate juice to protect against ED</a> called for a larger test to prove its efficacy, WebMD reports.

  • Yohimbe

    Mmm, bark. Prior to Viagra hitting the market, doctors would prescribe the bark of the African yohimbe tree to ED sufferers. While its ability to improve erections is questioned, doctors are no stranger to its <a href="">yohimbe's many scary side effects</a>, including increased blood pressure and irregular heart beat, according to WebMD.

  • Ginseng

    Live Science noted that ginseng was among one of the many <a href="">natural aphrodisiacs</a> that had the most potential to treat ED.

  • Gingko

    A recent study found that <a href="">ginko biloba extract does not prevent memory loss in those with Alzheimer's</a>, but it may help ED sufferers by increasing <a href="">blood flow to the penis</a>, according to Mayo Clinic.

  • Epimedium

    Also known by its snicker-inducing name horny goat weed, <a href="">epimedium has traditionally been used in Chinese medicine to treat ED</a>, according to the Mayo Clinic. However it warns that there has been little study into the herb's side effects, which include blood thinning and lower blood pressure.

  • Zinc

    For men with zinc deficiency, taking <a href="">the mineral may help with erectile dysfunction</a>, according to Mayo Clinic.

  • Acupuncture

    A recent survey of four studies found there wasn't enough evidence to prove that using the centuries-old practice to treat ED actually worked. But urologist Bruce Gilbert told Everyday Health acupuncture is worth a shot: "It probably works best to treat the psychological component of ED. There is very little downside to trying it."