Friday, November 01, 2013

Doctor Brain's laboratory

Insight, Advice - Mind, Body and Family, Nov '13
By Dr. Tirthankar Guha Thakurta

Prologue

The human body is aptly called a biochemical laboratory. Each time we discover the hidden codes that run the laboratory, we are left surprised at its precision and complexity. While speaking of the human ‘mind’, there is an age-long tug-of-war between biological and behavioural theorists (see The Mind-Body Riddle, September 2013 issue of Varta). It was identified long ago that our mind is a reflection of our brain’s activity and the mind cannot exist free from the body. It is as simple and perhaps as silly as two computer lovers fighting about the superiority of hardware and software over each other. Both fail to see that both are right about their theory, and both are wrong in ignoring the other. But the tug-of-war seems to entertain us till date.

The human brain is a magical tangle of neurons or nerve cells that can ‘feel, think and act’. Each nerve cell is like a branching tree that connects each of its branches to another nerve cell, forming an extremely complex network. Information flows through this network as electrical and chemical signals. The electrical signals can be measured by procedures like an electro-encephalography (EEG). The chemicals, however, are difficult to measure. With modern techniques we have gathered a large pool of data about these chemicals, suitably called neurotransmitters.

The number of neurotransmitters in our body exceeds a few hundreds. While all of them are equally fascinating to study, perhaps the most versatile and interesting brain chemical is dopamine. This chemical plays versatile roles in our body (and mind).

Dopamine: The magic molecule

Dopamine is a common chemical and its molecules are found in plenty in nature – from the pulp of a ripe banana to the brains of worms, fish, birds and mammals. Dopamine was first synthesised in a laboratory in 1910. But it was not until 1958 that we came to know the functions of this versatile chemical in controlling our behaviour.

Dopamine is found in different parts of the body, where it serves unique functions. In the parts of the brain that ‘think and feel’ (mesocortical and mesolimbic systems) it helps in love, affection, bonding, creativity, addiction and craving. In one of the many parts of the body that control movements (basal ganglia), it helps in planning and performing swift movements. In the hormone secreting parts of the brain (hypothalamo-pituitary axis), dopamine prevents the release of another chemical called prolactin, which helps in the secretion of breast milk. In the parts of the brain concerned with vomiting, dopamine provokes vomiting. In the heart, it raises the pumping force and increases blood circulation.

Dopamine is also a raw material for synthesis of other chemicals. These include the stress-hormones adrenalin and nor-adrenalin, the brown pigment of our skin (melanin) and some other chemicals. Too much or too little of dopamine can cause a host of psychological and physical discomforts. Some case histories follow (with names and locations changed).

Mr. X’s ‘false’ fears

Mr. X is a 29 year old school teacher. He lives with his parents and brother. For the past three months, he seemed a lot anxious. When he was brought to a psychiatric clinic by his brother, Mr. X said that he was victim to a big international conspiracy. There were people following him on the roads and satellites were being planted to monitor his activities. He did not eat for a whole day thinking that the food was poisoned. He could not, however, explain why he in particular was chosen as a victim. His brother was evidently concerned about Mr. X.

This relatively common condition that Mr. X experienced is called paranoid schizophrenia. The individual experiences false but firm fears of being harmed and controlled by others. This in turn affects the social and physical health of the person and his significant others.

It was a landmark discovery when it was observed that paranoid schizophrenia was associated with too much dopamine in the ‘thinking’ parts of the brain. We could soon develop a basketful of drugs that could prevent the action of too much dopamine in the brain. These drugs magically removed all signs of schizophrenia in most patients. This dopamine-theory revolutionised the treatment of schizophrenia and related disorders that once posed huge challenges to mental health professionals.

Mr. X was treated with one such drug (Olanzapine) and his false fears disappeared completely in a month.

Relief from vomiting

Ms. Y visited the emergency department of a hospital with severe vomiting. She ate outside food in the morning and started vomiting since the afternoon. She was diagnosed with food poisoning. While an antibiotic would kill the germs that were causing the symptoms, she needed a rapid and effective relief from the bouts of vomiting.

It is known that dopamine plays an important role in causing vomiting. Other chemicals like serotonin, histamine and neurokinins play equally important roles. Drugs that prevent the action of these chemicals effectively control vomiting in most individuals. Ms. Y was given an injection of a dopamine-blocking drug (metoclopramide). In 10 minutes she felt better.

Understanding the complex network of nerves and chemicals that cause vomiting has been a significant step ahead in medicine. From the cases of food poisoning to patients suffering migraine headache, vomiting is a common complaint. Patients fighting cancer with chemotherapy suffer from severe attacks of vomiting. Thanks to the understanding gained about the chemical codes of vomiting, they can now experience some relief.

Managing Parkinson’s Disease

Mr. Z is a 65 year old retired traffic sergeant. He was once famous for his terrific athletic abilities. Over the last one year he developed stiffness of body, trembling hands and experienced frequent falls while walking. He was diagnosed with Parkinson’s Disease.

Parkinson’s Disease is usually a disease of old age. It is caused by too little dopamine in the basal ganglia that control movements. In some individuals dopamine secreting nerves gradually disappear in the basal ganglia with age. Since dopamine helps in planning and performing swift movements, lack of sufficient dopamine makes the movement jerky and the muscles stiff. In severe cases the person fails to maintain balance and falls.

The discovery that Parkinson’s Disease is caused by reduced dopamine in brain prompted the discovery of many drugs that increase dopamine activity in the brain. These include levodopa, amantadine, selegiline, entacapone and many others. These drugs revolutionised the treatment of symptoms of Parkinson’s Disease. In very severe cases we can even implant a device in the brain through surgery. The device helps the patient send electrical signals to the necessary parts of the brain and overcome the symptoms of Parkinson’s Disease. This novel therapy is called deep brain stimulation.

Mr. Z was treated with levodopa, followed by entacapone. His symptoms reduced to a large extent.

Not the last word

Thanks for continuing to read! This is only a glimpse into the many functions of only one neurotransmitter chemical – dopamine. Imagine how spectacular it is when all the hundreds of neurotransmitters in our body, each unique in its own way, take part in a well-rehearsed orchestra when we feel, think or act!

Are we then slaves to the action of streams of chemical signals? What about volition and free will? Can we not make conscious choices in life?

Well, yes and no!

Yes, because we do make conscious choices in life. It is a fact that dopamine designs our addiction for something (say cocaine). But we can choose to go for rehabilitation and refrain from addiction for the rest of our life.

No, because even these conscious decisions are brought about by the release of neurotransmitters in our brain. We just choose a different lobby to help ourselves.

Confused? Disturbed? Just inquisitive? Write in any query on the mind, body and family to vartablog@gmail.com, and Dr. Tirthankar Guha Thakurta, teaching faculty at a Kolkata-based medical college, will be happy to answer them – with due respect to confidentiality.

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