Dopamine is a neurotransmitter that increases arousal and decreases inhibition in the brain. Variants in the DRD4 dopamine receptor gene have been linked to attention deficit hyperactivity disorder (ADHD). Methylphenidate, commonly known as Ritalin, is used to treat ADHD by increasing dopamine levels in the brain and improving concentration. Genetic differences that cause variants of the DRD4 receptor may help explain why certain behaviors are inherited.

1. Human Behaviour, Dopamine and DNA How the DRD4 receptor contributes to Human Behaviour

2. Dopamine Dopamine is both a neurotransmitter and a hormone. It is the precursor for adrenaline and noradrenaline production Dopamine increases arousal and decreases inhibition. Its effects would show up on a brainscan as increased cerebral activity

3. Problems associated with Dopamine Parkinsons disease is associated with very low levels of dopamine A surplus of dopamine is associated with a schizophrenic behaviour. Parkinson’s disease can be treated by administering Levodopa L-dopa is transformed into dopamine in the dopaminergic neurons of the sufferer Scan showing reduced activity in dopamine producing cells.

4. DRD receptors There are 5 types of DRD receptor in the brain which are complementary to dopamine. The different types are found in different locationS in the brain. As with all surface proteins these receptors are coded for by genes. Some genes produce a DRD4 receptor implicated in Attention Deficit Hyperactivity Disorder

5. Methylphenidate (Ritalin) ADHD sufferers have been shown to have a particular variant of the DRD4 dopmamine receptor Methylphenidate which shares a similar structure to dopamine is used to increase dopamine levels in the brain. This helps reduce the effects of ADHD improving concentration

6. Genetics and behaviour Because the variants of DRD4 are caused by difference in base sequence it may be that certain behaviours can be inherited. Lack of the neurotransmitter serotonin may be responsible for Obsessive Compulsive Disorder Surplus dopamine can lead to psychotic behaviour. Anti-psychotic drugs block DRD receptors.