Psychopharmacology Course

Psychostimulants Explained, Simply

A brief narrative of how dopamine and other monoamines act as musical "tuners."
In individuals with attention and/or concentration problems, there may be a problem with how the brain is processing sensory input.
 
Our brains spend an enormous amount of energy (up to 20-30% of all energy used by your body) processing information below our level of awareness.
 
In fact only a very small percentage of brain activity contributes to our conscious awareness, about 15% (rough estimate).
 
The rest of the activity is all the unconscious processing, integrating, and analyzing of information that ultimately results in complex behavior. Much of the brain’s energy is spent “deciding” which signals are relevant and need to be brought to conscious awareness.
 
Think of all the activities we do that we aren’t even aware of. While walking down the street talking with someone, do you actively feel your left big toe? Well, no, not unless you have pain or stub your toe.
 
We aren’t aware of our left big toe because it’s irrelevant to what we are doing. But this doesn’t mean those signals aren’t physiologically absent.
 
Dopamine, serotonin, and norepinephrine are monoamine neurotransmitters in the brain that act like the tuners of a piano. The actual piano itself can be thought of as the glutamate neurons, GABA neurons, and supporting cells within the brain that play the music. Glutamate and GABA neurons make up the majority of the neurons in the mammalian brain and only a small fraction are dopamine, norepinephrine, and serotonin (see chart below).
 
 
The monoamines, especially norepinephrine and dopamine (and many others including steroid hormones, etc) are there to tighten the strings so the music sounds good. No one likes a song that is off beat or out of tune.
 
Dopamine and norepinephrine are like those “tuners” of the brain–they modulate communication between neurons. They help your brain decide what you should ignore and what you should focus on.
 
 
Interestingly, ignoring and focusing may be two separate processes or systems in the brain. Medications like amphetamines (vyvanse, adderall), methylphenidate (Ritalin, concerta), bupropion (Wellbutrin), atomoxetine (strattera), and other medications modulate these monoamines (“tuners”) to help us tune out the extraneous signals coming in that we just don’t need while allowing the important relevant signals flowing smoothly.
 
Like a garden hose with holes in it, one monoamine system increases the water pressure while the other plugs the holes so the water gets to where it’s supposed to go.
 
Obviously the brain is much more complex than this example, but it gives us a framework for why our psychiatric medications might work.
 
Medications (or illicit drugs) that enhance dopamine too much in certain regions of the brain may cause us to “hyperfocus” or “fixate” our attention such that we find ourselves overly “motivated” to do things that might not yield a large reward at all.
 
On the other hand, too little dopamine in certain areas of the brain and we might lack motivation altogether and find ourselves apathetic or indifferent to doing anything because most tasks don’t seem “worth it” because the perceived reward isn’t big enough.

REFERENCES:

 

  1. Schatzberg, A. F., & DeBattista, C. (2015). Manual of clinical psychopharmacology. Washington, DC: American Psychiatric Publishing.
  2. Schatzberg, A. F., & Nemeroff, C. B. (2017). The American Psychiatric Association Publishing textbook of psychopharmacology. Arlington, VA: American Psychiatric Association Publishing.
  3. Stahl, S. M. (2013). Stahl’s essential psychopharmacology: Neuroscientific basis and practical applications (4th ed.). New York, NY, US: Cambridge University Press.
  4. Neuroscience, Sixth Edition. Dale Purves, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, Richard D. Mooney, Michael L. Platt, and Leonard E. White. Oxford University Press. 2018.
  5. Ebenezer, Ivor. Neuropsychopharmacology and Therapeutics. John Wiley & Sons, Ltd. 2015.
  6. Cooper, J. R., Bloom, F. E., & Roth, R. H. (2003). The biochemical basis of neuropharmacology (8th ed.). New York, NY, US: Oxford University Press.
  7. Iversen, L. L., Iversen, S. D., Bloom, F. E., & Roth, R. H. (2009). Introduction to neuropsychopharmacology. Oxford: Oxford University Press.

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