How do anti-depressants like Prozac, an SSRI work?

The serotonin system is the main target of all anti-depressants classified as SSRIs. SSRI stands for selective serotonin reuptake inhibitor. Prozac is the most well known.  In mood disorders such as depression, anxiety, but also aggression and sometimes post-traumatic stress disorder, there is not enough serotonin for the neurons to use.

This can happen for several reasons.

  1. A person is genetically programmed to produce less serotonin. This means the  pre-synaptic cell releases too small an amount of vesicles filled with serotonin. This may cause not enough neurons to fire. If not enough neurons fire, the mood enhancing aspects of serotonin will not be experienced.
  2. A person may have an extra fast breakdown of the neurotransmitter so that it also won’t cause a big effect in the next neuron. The serotonin gets sucked back into the pre-synaptic cells before enough was received by the post-synaptic side. The result is the same as above in which a lack of firing will not allow the mood enhancing aspects of serotonin to be enjoyed.

 

How does an SSRI help the situation?

The SSRI will cause the serotonin to remain longer in the synapse so the neighboring cell or post-synaptic cell can have enough time to “enjoy the benefits.”

SSRI

If there is more serotonin around then the serotonin will bind to a receptor on the post-synaptic cell causing charged ions to enter. When the ions enter, the charge of the neuron changes. This makes the cell is more likely to fire an action potential.

If a cell continuously fires then eventually it will send a messenger to the nucleus, the brain of the brain cell, to unravel the DNA and make some new receptors. The newly ordered receptors are shuttled back to the post-synaptic/dendrite side where they can help bind more serotonin. This will cause the cell to fire more.

Take home message:

The SSRI can increase cell communication in cells that communicate with serotonin. This is done by making sure the next cell in line gets enough serotonin to be activated.

The increase in serotonin communication will regulate our mood, sleep, and appetite and general well-being.

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