Neurotransmitters monamine

Lithium enhances the uptake of tryptophan and increases the synthesis of serotonin. It is also thought to decrease the reuptake of monamine neurotransmitters (e.g., catecholamines and serotonin). Reactions can be idiosyncratic, however, as lithium also decreases the conversion of thyroxine to triiodothyronine in the CNS. 

Here then is the logic behind the first version of the chemical-imbalance theory. Iproniazid is a monamine oxidase inhibitor - it inhibits the oxidation of norepinephrine and serotonin in the synapses, thereby leaving more of these neurotransmitters available in the brain. When depressed people take iproniazid, they get better. Therefore insufficient norepinephrine and/or serotonin causes depression.12... 

Monamines are inactivated into aldehydes by amine oxidase (monoamine oxidase, MAO ) with deamination and simultaneous oxidation. MAO inhibitors therefore play an important role in pharmacological interventions in neurotransmitter metabolism. 

Monamine Oxidase Inhibitors (MAOI). The enzyme monoamine oxidase inactivates norepinephrine, dopamine, epinephrine, and serotonin. By inhibiting monoamine oxidase, the levels of these neurotransmitters rise. Examples of these drugs includes isocarboxazid (Marplan), phenelzine sulfate (Nardil), and tranycypromine sulfate (Parnate). 

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