If you have ever been victimized by an ice cube down the back, you know that close encounters of the cold kind have an immediate effect on the human body.

The shiver along the spine, the squirm away from the ice, the excited epithet [eh-pih-thet] that escapes the lips… it all happens in a second, seemingly without thought.

Now, in chilling news from the University of Southern California, neuroscientists have unveiled the sensory strands responsible for our response to cold.

Until this study was published in a recent issue of the Journal of Neuroscience, no one had ever seen the actual route of a “cold” signal from icy inception to final shiver.

But by genetically engineering mice to produce a protein called T-R-P-M-8 with a trace of fluorescence, researchers were able to photograph sensory signals along glowing fibers that connect nerve endings at the body’s exterior to neurons near the spinal cord.

The cold-carrying protein is found in a subset of nerve cells that relays sensations ranging from stinging cold to soothing coolness.

Whether the chill was produced by menthol, ice or pain-relief lotions, researchers found that T-R-P-M-8 snapped into action.

Scientists hope that by learning more about the pathways and molecular mechanisms that underlie our senses, they will be able to develop better pain relievers.

But no matter what new wonders they discover in the nervous system, you have to admit, it still takes a lot of nerve to slip an ice cube down someone’s shirt.