Ritalin and D2 Receptors: Overview
Ritalin® (
methylphenidate hydrochloride) is a commonly prescribed medication approved for the treatment of
ADHD and
narcolepsy. It is also a commonly abused drug
(see Ritalin Abuse). Research suggests that the effectiveness of
Ritalin for ADHD and its potential for abuse are both related to its effect on dopamine in the brain.
Dopamine and D2 Receptors
Dopamine is one of several monoamine neurotransmitters in the brain. There are at least five types of dopamine receptors: D1, D2, D3, D4, and D5. Dopamine can have different effects when it is bound to different receptor types. D2 receptors have been linked to the reinforcing aspects of drug use. "Reinforcement" is the scientific word for the feelings (or changes in the brain) that lead people to repeat certain actions (such as abusing a drug). Animal studies have shown that drugs like
morphine and amphetamine do not have reinforcing effects in certain mice that do not have D2 receptors.
A great deal of research has been conducted on dopamine changes in people with ADHD. Some studies have shown that people with ADHD have too much dopamine transporter (DAT, for short) in a certain part of the brain called the striatum. DAT transports dopamine away from neurons in the striatum, and having too much DAT may lead to a dopamine deficiency in that part of the brain. Additional studies have suggested that dopamine in the striatum helps people to focus, and a dopamine deficiency (from too much DAT) could be partly responsible for the symptoms of ADHD.
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