When women are aroused, they overlook certain “disgust elicitors” associated with sex, enabling them to go ahead with the deed, according to a paper published by Dutch clinical psychologists.

According to the study, published in the journal PLoS, humans have somehow managed to strike a successful balance between two important evolutionary functions — sex and disgust. The latter is considered by some psychologists to be a natural defence mechanism against disease — other people’s mouths, for instance, pose a higher risk of contamination and are therefore considered an external threat perceived as highly disgusting. When it comes to the nitty gritty of sex, there are plenty of “disgust elicitors” that we relate to contamination says the paper, namely saliva, sweat and semen.

In making this link, the paper’s authors’ decided to tackle a rather interesting question: how do people have pleasurable sex at all?

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Smell the potassium: Surprising find in study of sex- and aggression-triggering vomeronasal organ

"We found two new ion channels—both of them potassium channels—through which VNO neurons are activated in mice," says Associate Investigator C. Ron Yu, Ph.D., senior author of the study. "This is quite unusual; potassium channels normally don’t play a direct role in the activation of sensory neurons."

Humans have shrunken, seemingly vestigial VNOs, but still exhibit instinctive, pre-programmed behaviors relating to reproduction and aggression. Scientists hope that an understanding of how the VNO works in mice and other lower mammals will provide clues to how these innate behaviors are triggered in humans.

The VNO works in much the same way as the main olfactory organ that provides the sense of smell. Its neurons and their input stalks, known as dendrites, are studded with specialized receptors that can be activated by contact with specific messenger-chemicals called pheromones, found mostly in body fluids. When activated, VNO receptors cause adjacent ion channels to open or close allowing ions to flood into or out of a neuron. These inflows and outflows of electric charge create voltage surges that can activate a VNO neuron, so that it signals to the brain to turn on a specific behavior.