HOT STUFF: Capsaicinoids are the compounds that give chili peppers their spicy taste. They bond with pain receptors in the mouth and throat, producing a burning sensation in the tissue. Then the receptors send a message to the brain, which triggers increases in heart rate and perspiration, as well as the release of endorphins (which are also released in other situations that play with the sensations of pleasure and pain, such as the runner's high). The units used to describe the heat of a pepper are called Scoville heat units (SHU). Bell peppers rank 0 SHU, jalapenos 3,000-6,000, habaneros 300,000, and the naga jolokia (a pepper from India) ranks the highest, with over 1,000,000 SHU.