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These Rats Get Instant Erections When Bathed in Blue Light

A brand new way to get blue balls.
​Image: Martin Fussenegger

​Generally, erectile dysfunction is treated with a blue pill. Now, scientists are trying to treat it with a blue light, using a process in which the light is shined on your penis to reflexively induce an erection in an attempt to "decouple penile erection from natural stimuli and neural-system control."

Wait, what?

​Optogenetics is a burgeoning field of synthetic biology in which certain neurons and body processes can be controlled using light. Typically, light-sensitive algal or bacterial DNA is encoded into a virus that targets specific neurons in the brain. That virus is then injected into the brain of whatever you want to control, usually a mouse or rat (though there's no reason it couldn't work in humans—​it hasn't been tried yet because of ethical concerns). This "transfection" then allows you to turn those neurons off and on using a blue light.


A blue light-induced rat erection. Image: Martin Fussenegger

As I mentioned, usually optogenetic manipulation is done in the brain. But it can also be done in the penis, specifically on a region of it known as the ​corpus cavernosum, the part that fills with blood during an erection.

During normal erections, the muscles surrounding the corpus cavernosum relax, allowing blood to flow in. But an erection is a very complicated thing—circulatory problems, depression, nervousness, racing thoughts, a lack of testosterone, and so on can prevent the release of the hormones and nitric oxide necessary to properly induce an erection.

Once you actually have an erection, you can lose it through the degradation of an enzyme known as cGMP, which regulates blood flow into and out of the penis. Viagra slows down that degradation, allowing you to maintain an erection, but it doesn't actually induce an erection without sexual stimuli. Optogenetics, on the other hand, can be used to trigger erections without any other stimulus.

Martin Fussenegger, a researcher at the Swiss Federal Institute of Technology in Zurich, ​published a paper last week in Angewandte Chemie (a journal published by the German Chemical Society), in which he details a process to use optogenetics to stimulate erections in rats.

He calls it an "erectile optogenetic stimulator," and it's quite simple, once you get past the gene-therapy part of it. Shine a blue light (a Philips goLITE BLU, designed to treat seasonal affective disorder, if you must know) on a rat dick, cause dick to get hard.


He transfected rats by injecting their corpa cavernosa with the light-sensitive DNA from a bacteria—after a series of different gene variants, some of which were tossed out because of "leakiness," he found one that reliably caused erections.

"The EROS-treated rats showed different levels of erectile response within 55 seconds upon exposure to blue light, ranging from tumescence of the tip of the glans (duration: 11 seconds) to erection (duration: 37 seconds) and ejaculation," he wrote in the paper.

Notably, no female mice were in the test room, he added.

Further tests showed that the blue light was indeed causing the muscle relaxation the scientists were aiming for, and a second treatment of Viagra "significantly increased blue-light-induced EROS-triggered relaxation."

Fussenegger told me that he used wild rats, not genetically altered ones, as is common in optogenetic experiments. He wrote in the paper that the penis has "straightforward accessibility" that makes it an "ideal target for the direct delivery of naked DNA" necessary for transfection.

Image: Martin Fussenegger

The plan is to eventually use this either instead of or in tandem with Viagra to treat erectile dysfunction and give men access to on-demand erections.

"The current treatment strategies focus either on restoring erection-promoting pathways or maintaining an established erection but fail to provide a trigger-inducible erection on demand," he wrote.

"EROS decouples penile erection from physiological control, bypasses the causes for erectile dysfunction, and providers trigger-inducible erection on demand by simple illumination with a portable commercial light-therapy device," he added.

The sex toy of the future, then, might be a little blue light.