Until recently all that was known about how antidepressants work is that they maintain a balance of brain chemicals called neurotransmitters. What was not known was how antidepressants bind to brain cells for the antidepressant to work.

Medications, called tricyclic antidepressants, help offset the imbalance of the neurotransmitters serotonin and norepinephrine. They accomplish this by not allowing the neurotransmitters to flood back into the brain cells that emit them, which makes the neurotransmitters available to other cells. By redirecting the neurotransmitters helps relieve depression in patients. How the medications shut down the pumps at the molecular level remained a mystery until recently.

Researchers used bacteria with a pump that operates almost identically to the one in the brain cells, but changes in its molecular structure are easier to analyze.

Experiments shows that tricyclic antidepressants latch onto the bacterial pump, changing its molecular structure in a way that effectively stops the pumping action. Now that scientist know that plugging these kinds of pumps is one way to reduce their activity, researchers may be able to develop medications that target them more directly and efficiently. This could result in more effective antidepressants with fewer side effects. The findings may also extend to the development of medications for other mental illnesses in which pump dysfunction plays a role.