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BERKSHIRE AD/HD RESEARCH GROUP DNA-RESEARCH PROJECT

During 1937 a Rhode Island Pediatrician reported that administering stimulants to children with AD/HD had the unexpected effect of calming them down. In the 1990s the stimulant Ritalin has become the most prescribed drug for this condition. Scientifically, we know that Ritalin works through release of the powerful brain chemical messenger, Dopamine. Dopamine interacts with a family of brain receptors (Dl, D2, D3, D4, D5) most profoundly with the D2 type.

AD/HD is GENETIC:

A converging body of evidence from lesion studies in animals and humans, brain imaging studies, EEG studies, responses to medication and genetic studies supports the premise that AD/HD is primarily biologically based. The predominance of evidence points towards involvement of the frontal-strictly system of the brain. What researchers do say with great certainty is that the condition is inherited, the influence of genes is unmistakable.

The biology behind AD/HD is beginning to surface. 'We cannot say which structure or which chemical is wrong" emphasizes Alan Zametkin of the National Institute of Mental Health (NIHM), however, a subset of AD/HD sufferers have a different receptor for thyroid hormone and that 70 - 80% with this rare difference in their thyroid receptor have AD/HD. Studies have found an association between AD/HD and three genes encoding receptors for the neurotransmitters Dopamine. Collaborating with molecular biologists and geneticists at Irvine and at the University of Toronto, Swanson examined the so called novelty seeking gene, which codes for the Dopamine receptor DRD4. One series of base pairs repeats two, four or seven times. More repeats are associated with a blunted response to Dopamine signals and less inhibited behavior. We found that the seven repeat variety of the gene is over-represented among AD/HD children. Russell Barkley also estimates that 40% of AD/HD children have a parent who has the condition."

Scientists have also discovered structural abnormalities. F. Xavier Castellanos of the NIMH used magnetic resonance imaging to measure the total brain volume and several different brain regions in 57 AD/HD boys and 55 healthy control subjects. His team found that the anterior frontal part of the brain was on average more than 5% smaller on the right side in AD/HD boys. The right cudate and the globus pallidus, too, were smaller. These structures form the main neural circuit by which the cortex inhibits behavior, and so damage three might well manifest itself as a lack of impulse control.

Another facet of AD/HD malfunctioning comes from positron emission topography PET studies. The PET scanning device (which is not used in the UK for aiding diagnosis - most probably due to costs) shows the deficiencies in Dopamine levels in AD/HD sufferers.

Neurotransmitters and Receptors:

Neurotransmitters are manufactured in the neuron from amino acids and the supply is controlled by enzymes that have the capacity to destroy neurotransmitters. Normally enzymes keep the supply of neurotransmitters in balance with the demand for normal cell activity. There are two types of neurotransmitters: monoamines and neuropep tides.

Monoamines:

Monoamines are made of single amino acids derived from food and carried by the blood into the brain.

Serotonin:

Its effects are many and varied. Serotonin promotes feelings of well being and helps us sleep. It reduces feelings that lead to aggression and compulsive behaviors. Serotonin also elevates the pain threshold and helps protect the heart.

Dopamine:

Dopamine increases feelings of well being and alertness. It also decreases the desire for compulsive behaviors. An excess of Dopamine can lead to irrational behavior or aggression.

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