Serotonin and Treatments for Depression, Animation.


Serotonin, or 5-hydroxytryptamine, is a neurotransmitter
involved in many brain and body functions and is commonly known as the substance of
well-being and happiness. Serotonin is produced in specialized neurons
found mostly in the Raphe nuclei located along the midline of the brainstem. The axons of
these neurons form extensive serotonergic pathways that reach almost every part of the
central nervous system, including the cerebellum and the spinal cord. This is why it’s not
surprising that serotonin is implicated in a vast array of brain functions, including
sleep and wake cycle, appetite, mood regulation, memory and learning, temperature control,
… among others. Serotonin is synthesized from the amino acid
tryptophan and is stored in small vesicles within the nerve terminal. When a serotonergic
neuron is stimulated, serotonin is released into the synaptic cleft where it binds to
and activates serotonin-receptors on the postsynaptic neuron. Serotonin action is then TERMINATED
via removal of its molecules from the synaptic space. This is accomplished through a special
protein called serotonin-transporter. Low levels of serotonin in the brain have
been associated with depressive disorders and current treatments for depression aim
to increase these levels. The most commonly prescribed medications, called “selective
serotonin reuptake inhibitors”, or SSRIs, act by blocking serotonin reuptake by the
transmitting neurons. This results in elevated levels of serotonin in the synaptic space
and its prolonged action on the receiving neuron. The SSRIs have developed into the
drugs of choice because they produce fewer side effects thanks to their selective action
on serotonin alone and no other neurotransmitters. Unfortunately, because serotonin is involved
in a wide range of brain functions, the side effects remain significant and may progress
to a potentially dangerous condition known as “serotonin syndrome”. This syndrome is
generally caused by a combination of two or more drugs used to raise the serotonin levels
in the brain. If the medications are not discontinued, the condition may become fatal.
Nonpharmacologic methods of raising brain serotonin have shown promising results in
recent studies. It has been suggested that positive mood induction, either self-induced
or due to psychotherapy, correlates with INCREASED serotonin synthesis in the brain. The interaction
between serotonin synthesis and mood may therefore be 2-way, with serotonin influencing mood
and mood influencing serotonin. Other methods include exposure to bright light
and tryptophan-rich diets. To note, however, that serotonin-rich food such as bananas would
NOT work because serotonin, unlike tryptophan, can NOT cross the blood brain barrier.
Finally, although it sounds like a cliché, physical exercise maybe the most effective
and safest way of improving mood. Several studies suggest that serotonin levels are
increased with vigorous physical activity and that these elevated levels are maintained
for several days after the exercise.

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