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Neurotransmitters:

the reason behind depression, addiction and all sorts of other brain-related phenomena

You know that most every action in your body – writing your name, saying hello, kicking a ball, playing the piano - involves neurons in the brain sending electrical signals to each other. When those signals are sent, an electrical impulse travels from the axon of one cell to the dendrite of another. This signal has to cross a small gap called a synapse. Chemicals called neurotransmitters, produced in the nerve cells themselves, are the chemical messengers that carry these signals from one cell to another.We’ll model neurotransmitters with Smarties!!

There are many different neurotransmitters. Two of the most interesting are dopamine and serotonin. You’ll recall that dopamine is the brain’s “pleasure chemical”; serotonin is a chemical that plays a large role in mood regulation and depression.

Dopamine is produced in our midbrain whenever we do something that aids our survival either as individuals (eating, winning, acquiring possessions) or as a species (reproducing, helping others)etc. Dopamine then helps conduct signals through a pathway in our brain called the reward pathway – when dopamine is produced, we feel good.

We’ll arrange some of our neurons as part of a dopamine pathway.

Using your neuron models, try to model these steps in the normal dopamine process:

  1. Dopamine is made in a cell body.
  2. Dopaminetravels down the axon to the synapse.
  3. Dopamine is released from the cell and floats into the synapse.
  4. Dopamine in the synapse allows the electrical signal to pass from one cell to the next.
  5. Some dopamine is broken down in the synapse.
  6. Some dopamine is taken back into the original cell and recycled (this is called “re-uptake”).

What are some things that might go wrong in the process you just modeled that may result in low levels of dopamine?

There is some indication that low levels of dopamine may be responsible for some forms of depression or for ADHD.

The ADHD medication Adderall, for example, is thought to speed step #1 and slow step #5

Certain antidepressantslike Wellbutrin work by slowing the process in #6, above.

This keeps dopamine in the synapses longer.

We will model Wellbutrin’s action with raisins.

Wellbutrin molecules block some of the reuptake of dopamine; set up a model of what this might look like in a synapse.

The longer dopamine stays in your synapses, the happier you feel!

So far so good…but here’s the problem:

Cocaine dramaticallyblocks the reuptake of dopamine.

Use your materials to show what happens in a synapse under the influence of cocaine.

We will represent dopamine with Smarties.

We will represent cocaine with Navy Beans.

After the cocaine has worn off, how do you think your dopamine-producing brain cells respond?

In terms of dopamine, then, why do people become addicted to cocaine?

Another important neurotransmitter is serotonin. Normal levels of serotonin cause feelings of contentment and well-being. Low levels of serotonin are a major factor in many forms of depression.

Serotonin is also produced in parts of your midbrain and allows signals to be transmitted along reward pathways.

Most antidepressants (Prozac, Zoloft, Paxil) are selective serotonin reuptake inhibitors (SSRI’s). Think carefully about what each of those words means.

  • Use your materials to model how an SSRI affects serotonin in your synapses.
  • This time, your Smarties will represent molecules of serotonin.
  • We will represent an SSRI with sunflower seeds.

Finally, The drug Ecstasy is believed to have two effects on your brain cells

  • It causes higher production of serotonin.
  • It blocks the reuptake of serotonin.

Use your materials to model how Ecstasy would affect your synapses. We will represent Ecstasy with pushpins.

What then is the effect of Ecstasy on someone’s mood?

After the Ecstasy has “worn off”, how do you think brain cells might respond?

Here is some information about these and other neurotransmitters:

Neurotransmitter / Function / Too much? / Too little? / Notes
Serotonin / Promotes contentment / Mania? / Depression / Ecstasy blocks serotonin reuptake.
Norepinephrine / Causes alertness, contentment / “Excessive” alertness – being “wired” / Fatigue, depression / Nicotine causes release of this.
Dopamine / Feelings of contentment; dopamine is often produced as a reward by our brain after we do something that aids our survival (eating, winning, procreating) / Schizophrenia / Depression? / Cocaine, amphetamines block reuptake, keeping dopamine in our synapses, causing pleasurable feelings. The body responds to excess dopamine by destroying it, and when the high has worn off, there is not enough dopamine, and your body craves more. Thus, you become addicted to this feeling and to the drug that helps you produce it.
Endorphins / Natural painkillers released in times of severe pain. / Morphine and heroin mimic the effect of endorphins, cause addiction as above.
GABA / Keeps nerve cells from firing too much, helps you relax. / Overactive neurons – epileptic seizures? / Anesthetics greatly enhance GABA’s depressing effect.
Acetylcholine / Keeps nerve cells from firing too much, helps you relax, may help initiate sleep. / Alzheimer’s Disease / Nicotine also causes release of this.
Adenosine / Keeps nerve cells from firing too much, helps you relax. / Sluggishness, slow responses / High level of brain activity / Caffeine blocks out Adenosine, causes high level of brain activity.

Serotonin - Smarties

Ecstasy - pushpins

Wellbutrin– raisins

SSRI’s –sunflower seeds

Dopamine - Smarties

Cocaine – Navy Beans