Heroin

• Heroin is an illegal and highly addictive opiate from the same family as morphine and opium. The drug is derived from poppies and is sold as both a powder and as a sticky, black tar-like substance. Heroin users may sniff the drug in powder form, smoke it, or dilute the drug with water and inject it directly into the veins. Users often describe the heroin high as an initial surge of euphoria, followed by a warm, heavy feeling -- like slipping into a warm bath.
  
  

The Brain

• The brain controls the entire body with a complex series of chemicals called neurotransmitters. The brain releases these chemicals, which then attach to special sites called neuroreceptors. These sites exist within the brain and on the nerves that exit the brain, out to the rest of the body. Neurotransmitters come in different shapes, to correspond with specific neuroreceptors -- like a lock and key. A neuroreceptor "lock" can only accept a neurotransmitter "key" if it is the correct shape and size. When the key sits in the lock, it activates the nerve to perform its specific function. The brain controls how much neurotransmitter is released, and when. For example, the brain only releases neurotransmitters for pain when the body is injured.
  
  

Heroin and the Brain

• Heroin has the exact shape and size as a neurotransmitter called an endorphin. Endorphins are the body's "feel good" chemical, which the brain releases in response to pain and stress. The brain and body have natural receptors for endorphins and because heroin is the same shape and size, it fits neatly into those receptors. The effect of heroin is more intense than the body's own endorphin because the brain has no control over the amount of heroin that hits the receptors. The brain does not produce the amount of endorphin needed to simulate the heroin high. When the heroin wears off, the addict needs to use it again to achieve that same rush.
  
  

Heroin Addiction

• The brain doesn't differentiate between chemicals it creates and external chemicals that serve the same function. The brain also needs to maintain balance in the body. If you introduce large quantities of a chemical that mimics an existing brain chemical, like heroin, the brain adjusts to maintain balance -- it produces less of the naturally occurring chemical and reduces the number of receptors. This means that the addict has to use more heroin more often to get the same effect. If he stops using heroin, he will start to feel pain, anxiety and other symptoms because the brain isn't producing endorphins. The addict has to continue using the heroin, not only for the high, but to avoid getting sick. However, eventually the brain will recover, and if the addict stops using, the brain will adjust its receptor levels and start producing endorphins again.