Smell the potassium

The vomeronasal organ (VNO) is one of evolution’s most direct behavior enforcers. From its niche within the nose in most land-based vertebrates, it detects pheromones and triggers corresponding basic-instinct behaviors, from compulsive mating to male-on-male death matches. A new study by Associate Investigator C. Ron Yu, PhD, and his team extends the scientific understanding of how pheromones activate the VNO and has implications for sensory transduction experiments in other fields.

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 the brain to turn on a specific behavior.

“We found two new ion channels—both of them potassium channels—through which VNO neurons are activated in mice,” explains Yu. “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 study was published in the September 15, 2012, in Nature Neuroscience.