Tricyclic antidepressant - Wikipedia, the free encyclopedia

The exact mechanism of action is not well understood, however it is generally thought that tricyclic antidepressants work by inhibiting the re-uptake of the neurotransmitters norepinephrine and serotonin by neurons. Tricyclics may also possess an affinity for muscarinic and histamine H1 receptors to varying degrees. Although the pharmacologic effect occurs immediately, often the patient's symptoms do not respond for 2 to 4 weeks.^[4] Although norepinephrine and dopamine are generally considered stimulatory neurotransmitters, tricyclic antidepressants also increase the effects H1 histamine, and thus most have sedative effects.^[5]

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The chemical action of re-uptake inhibitors in general was unknown for a long time. In August 2007, two research groups independently reported that the tricyclic molecule docks to the transporter protein in a cavity adjacent to where the neurotransmitter substrate binds, locking the substrate in place and thereby obstructing re-uptake transport.^[6]

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