The use of acupuncture is based on the belief that a vital life force, called chi (pronounced chee) flows through the body through a series of pathways known as meridians. Stimulation of points along these pathways causes the body to release natural pain relief chemicals called endorphins. Other effects produced may involve the release of anti-inflammatory and euphoric substances, increased circulation and decreased inflammation. Neurotransmitters, serotonin and prostaglandins are other substances that have physiologic effects and may be influenced under the stimulation of acupuncture. The precise mechanisms are unknown, but the goal in acupuncture is to balance chi, to increase it in some meridians and decrease it in others. Unbalanced chi is thought to be the cause of disease.