Remember the stops along a subway system, where we can hop off to make a phone call, that is, to send a message? Imagine that estrogen has the ability to send a text message via cell phone. Estrogen helps direct the creation of the structures we mentioned earlier, and it also sends those biochemical messages. The biochemical messages, much like the text messages of our cell phone, are sent via chemicals known as neurotransmitters. Just as we need to have the right phone number to send the text message, we also need to have the correct neurotransmitter.

A neuron releases neurotransmitters into a gap called the synaptic cleft where they are picked up by another neuron. Among other things, this communication between neurons regulates mood and behavior. Our mood can be altered when the level of these neurotransmitters fluctuates outside their normal levels, which may vary for each individual. Mood also depends on how many of the neurotransmitters are created, broken down, or left in the synaptic cleft. Again, it is similar to the cell-phone call. When you are having a bad day and call your best friend, she can cheer you up. But if you call the wrong number, a stranger will most likely hang up on you. The correct phone number, or coded neurotransmitter, can make a substantial difference in your mood.

One of the functions of estrogen is to alter the concentration and availability of several neurotransmitters involved in the regulation of mood. These neurotransmitters include dopamine, norepinephrine, acetylcholine, glutamate, GABA (gamma-aminobutyric acid), and serotonin. By controlling the creation, release, and breakdown of these neurotransmitters, estrogen acts similarly to antidepressants (Halbreich and Kahn 2001; Payne 2003). So estrogen may regulate depression and serve as the brain’s natural antidepressant simply due to its influence on neurotransmitters.

excerpt from The Estrogen-Depression Connection by Karen J. Miller Ph.D., Steven A. Rogers Ph.D.