<P> Dopamine receptors have been recognized as important components in the mechanism of ADHD for many years . Drugs used to treat ADHD, including methylphenidate and amphetamine, have significant effects on neuronal dopamine signaling . Studies of gene association have implicated several genes within dopamine signaling pathways; in particular, the D variant of D has been consistently shown to be more frequent in ADHD patients . ADHD patients with the 4.7 allele also tend to have better cognitive performance and long - term outcomes compared to ADHD patients without the 4.7 allele, suggesting that the allele is associated with a more benign form of ADHD . </P> <P> The D allele has suppressed gene expression compared to other variants . </P> <P> Dopamine is the primary neurotransmitter involved in the reward pathway in the brain . Thus, drugs that increase dopamine signaling may produce euphoric effects . Many recreational drugs, such as cocaine and substituted amphetamines, inhibit the dopamine transporter (DAT), the protein responsible for removing dopamine from the neural synapse . When DAT activity is blocked, the synapse floods with dopamine and increases dopaminergic signaling . When this occurs, particularly in the nucleus accumbens, increased D and decreased D receptor signaling mediates the "rewarding" stimulus of drug intake . </P> <P> While there is evidence that the dopamine system is involved in schizophrenia, the theory that hyperactive dopaminergic signal transduction induces the disease is controversial . Psychostimulants, such as amphetamine and cocaine, indirectly increase dopamine signaling; large doses and prolonged use can induce symptoms that resemble schizophrenia . Additionally, many antipsychotic drugs target dopamine receptors, especially D receptors . </P>

Where are the dopamine receptors located in the brain