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Brain Waves

« The Chemical Architecture of the Mind | Main | Post-Genome Pharmacology »

September 23, 2003

The Pharmacological Approach to Brain Mapping

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Posted by Tom

by Tom Ray

  1. Why are there so many different neurotransmitter receptors in the brain?
  2. What is the functional role of each, and how are they organized in the brain?
  3. How are the activities of these transmitter systems and their interactions associated with mental states?

In short, what is the chemical architecture of the brain and the mind that emerges from it? The answers to these questions should ultimately provide a firmer basis for understanding mental illness and developing treatments.

The pharmacological approach to these questions is to develop compounds that bind selectively at receptors, and activate or block them, and use them as probes to receptor function. When the molecular mechanisms of action of a drug are known, they can be correlated with the behavioral effects in animals or the subjective reports of humans, to understand the mental correlates of their underlying biological effects. When used in this way, pharmacology is a means of exploring the chemical organization of the brain and mind.

Peter Kramer's book "Listening to Prozac" introduced the pharmacological approach to the general public. The title "Listening to Prozac" means that we learned something new about the nature of the human mind by observing the effects of prozac.

Prozac was developed to treat depression, but when it was prescribed to large numbers of people, it was discovered that it also changed personality (from timid to self-confident). Before this unplanned experiment, it was not known that such aspects of personality were under chemical influence. By listening to prozac, we learned something about the chemical organization of the human mind.

Although pharmacology is generally thought of as a branch of medicine that uses chemicals to treat illness, pharmacology can also be used as a method of probing living systems to understand how they are organized and how they function.

Comments (2) | Category: Neuropharma


1. Zack Lynch on November 6, 2003 8:45 PM writes...

Tom: What are your best estimates regarding the three questions you proposed here?

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2. Tom Ray on November 7, 2003 9:50 PM writes...

Posted from an email from Tom:


I present these as big open questions in biology, and I don't presume to know the answers. Yet you ask me to answer them, so all I can do is to offer wild speculation.

> Why are there so many different neurotransmitter receptors in the brain?

It can be seen as a case of "differentiation". Differentiation usually supports functional specialization. Each of the several hundred receptors in the brain is produced by a different gene (in a few cases one gene produces more than one receptor due to differential splicing). The different genes can be independently regulated. Populations of receptors increase and decrease due to up and down regulations of the genes that produce them. It is one of the ways that neurons respond to the signals they receive. More receptors permit more complex responses, and allow a more complex neural organization.


This requires a case by case analysis, which is not appropriate here.

> How are the activities of these transmitter systems and their
> interactions associated with mental states?

There is some evidence that brains are "scale free networks". Most neurons send signals to a few other neurons, and fewer and fewer neurons send signals to more and more other neurons. The neurons that influence the greatest numbers of other neurons are of special interest.
These can be thought of as special modulatory neurons, which have a large influence on the state of the brain. These tend to be the major amine transmitter systems, using the neurotransmitters serotonin,dopamine, and norepinephrine. It appears that these are the
systems that regulate moods and emotions.

Tom Ray

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