Derived from the Asian opium poppy plant, heroin is an opiate. The National Institute on Drug Abuse reports that the National Survey on Drug Use and Health shows 213,000 people ages 12 and over in the United States have used heroin. When a person takes heroin, it converts into morphine once it crosses the blood-brain-barrier, a protective layer around the brain. Heroin use causes changes in the brain that results in addiction.
Binding to Opioid Receptors
When people use heroin, the drug binds to opioid receptors in the brain. The Canadian Institutes of Health Research notes that heroin attaches itself to the same receptors used by natural opiates produced by the brain, such as dynorphin, endorphins and enkephalins. When these opiates occur naturally, they can help with pain and cause people to feel good. But heroin intensifies these feelings, resulting in the euphoric rush that abusers use the drug for. When the effects of heroin wear off, users can feel drowsy.
Affecting GABA Levels
Heroin use also interferes with the neurotransmitter gamma-aminobutyric acid, or GABA. Canadian Institutes of Health Research points out that this occurs when heroin attaches to the mu receptors, one type of opioid receptor in the brain. Binding to the mu receptor reduces how much GABA that the brain releases. With less GABA in the brain, the brain has an increase in dopamine, a neurotransmitter linked to pleasure. The increase in dopamine also contributes to the euphoric feelings.
Inhibiting CAMP Production
The Canadian Institutes of Health Research explains that when people abuse heroin, it inhibits the production of the second messenger cyclic adenosine monophosphate, or cAMP. As a second messenger, cAMP relays information in the cells of the brain. When people stop using heroin, the levels of cAMP increase in the brain, causing people to have cravings for heroin.
Tolerance and Physical Dependence
As a person continues to use heroin, she builds up a tolerance to the drug. To get the same euphoric effects as before, people need to use more heroin. The brain gets accustomed to the effects of heroin and does not produce as many natural opiates as it did before. Through continued use, heroin users develop a physical dependence on the drug. The National Institute on Drug Abuse notes that 23 percent of heroin users become dependent on the drug. When people stop using heroin, they have withdrawal symptoms.
