Neuropeptides are small, protein-like molecules that help neurons communicate with each other. They contain anywhere from three to 40 amino acids and are found in the central nervous system, as well as in the peripheral nervous system. Acting as messengers in the body, neuropeptides perform specific functions. These molecules influence activities in the brain and body, such as analgesia, food intake, learning and memory.

Versatility is one characteristic of neuropeptides. They can transmit signals with information in several directions and in reverse. Neuropeptides can also work as hormones, neuromodulators, and neurohormones. When acting as neuromodulators, neuropeptides can activate and deactivate other neurotransmitters.

A person’s mood, energy level, pain, pleasure, weight, cognitive reasoning, ability to form memories, and immune system regulation are tied to neuropeptides. They can turn on cellular function in the skin. Neuropeptides can also be pro-inflammatory or anti-inflammatory. An anti-inflammatory neuropeptide may be beneficial to the body as it reduces inflammation, increases collagen and elastin, repairs scars and wrinkles, and increases circulation. People with glowing and radiant skin generally are reaping the benefits of anti-inflammatory neuropeptides.

Derived from the term "endogenous morphine", endorphins are a type of neuropeptide. They act as natural pain killers by blocking Substance P in the central nervous system. Substance P is another neuropeptide that transmits pain-related information from the peripheral nervous system to the central nervous system.

Endorphins play a role in memory, learning, sexual activity, and body temperature control. Some people experience the effects of endorphins when they run — called a runner’s high. The most euphoric reaction is caused by the neuropeptide beta-endorphin. Enzymes in the body break up endorphins, therefore making their effects short term.

Dr. Candace Pert, a psychopharmacologist and professor at Georgetown University in Washington, D.C., discovered that receptor molecules and the neuropeptides that bind to them exist in every part of the body, not just in the brain. This discovery means that mood-altering neuropeptides are present in the blood, muscles, bones, and organs. Many scientists believed emotions occurred as a response to a signal from the brain. Dr. Pert's research proved that emotional responses occurred at the cellular level.

Other breakthroughs in the study of neuropeptide research include an experiment conducted at the Toronto Hospital for Sick Children. The study demonstrated a possible link between neuropeptides and the development of type 1 diabetes. Scientists injected capsaicin, which triggers the release of neuropeptides, into non-obese diabetic mice that were genetically predisposed to develop type 1 diabetes. The injections killed the pancreatic sensory nerves and reduced the development of diabetes by 80 percent.