PDE-5 is the enemy.
This is the chemical that is released when your body decides it’s time for your erection to disappear. When you first start to get a stiffy, neurons produce nitric oxide, which begins a somewhat complicated chain of events resulting in the muscle tissue in your wiener being hit with something called cGMP. This enzyme relaxes the muscle walls (pecker-muscles are shaped like little bitty tubes) which can then flood with blood, resulting in a boner. Later, the buzz-killing PDE-5 comes along and breaks down the totally awesome cGMP, causing your pecker muscles to constrict once more and push the blood back out of your willy. Boner-pills such as Viagra, Cialis and Levitra all work by suppressing PDE-5, so once you get it up, it stays up until the drug wears off.
Given that all other disease in the the world has been pretty much cured, the good folks at the Medical College of Georgia decided that where they could do the most good in the world was by making an even better boner pill. Fortunately for them, they had a confederate in the Brazilian Wandering Spider. This industrious arachnid delivers a bite that is not only painful, but also bestows upon its victim a gigantic woody. (Perhaps the idea is that the bitten man will suddenly be too busy hunting bald ((waxed)) vaginas to concentrate on smooshing a cute, widdle ‘pider.)
The Brazilian’s toxin contains a peptide called Tx2-6, which causes nitric oxide to be produced, and yadda, yadda, yadda… they went out for breakfast in the morning. The drug researchers want to combine the Tx2-6 and the PDE-5 suppressors to create a master race of super-penises that will take over the world and make them feelthy rich. To this end they have been experimenting on tiny mouse boners, injecting them with the cocktail and measuring nitric oxide levels with even tinier needles they stick into the mousey wee-wees. (If you listen close, you can hear me screaming in the distance.)
For my part, I am proud such noble science is being pursued for the betterment of mankind. Additionally, I welcome our new penis overlords, and would encourage you to do the same.