Norepinephrine

Norepinephrine, known as noradrenaline outside the USA, is a catecholamine and a phenethylamine with chemical formula C8H11NO3. It is released from the adrenal glands as a hormone into the blood, but it is also a neurotransmitter in the nervous system where it is released from noradrenergic neurons during synaptic transmission. It is one of the 'stress hormones' and affects parts of the human brain where attention and impulsivity are controlled. Along with epinephrine this compound effects the fight-or-flight response, activating the sympathetic nervous system to directly increase heart rate, release energy from fat, and increase muscle readiness.

Antidepressants

Changes in the norepinephrine system are implicated in depression. SNRIs treat depression by increasing the amount of serotonin and norepinephrine available to postsynaptic cells in the brain. There is some recent evidence that the norepinephrine transporter also normally transports some dopamine as well, implying that SNRIs may also increase dopamine transmission. This is because SNRIs work by preventing the serotonin and norepinephrine transporter from taking their respective neurotransmitters back to their storage vesicles for later use. If the norepinephrine transporter normally recycles some dopamine too, then SNRIs will also enhance dopaminergic transmission. Therefore, the antidepressant effects associated with increasing norepinephrine levels may also be partly or largly due to the concurrent increase in dopamine (particularly in the prefrontal cortex).

Related Topics:
Depression - SNRI - Serotonin - Postsynaptic - Brain - Norepinephrine transporter - Dopamine - Neurotransmitter - Dopaminergic - Antidepressant - Prefrontal cortex

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Some other antidepressants (for example some tricyclic antidepressants (TCAs)) affect norepinephrine as well, in some cases without affecting other neurotransmitters (at least not directly).

~ ~ ~ ~ ~ ~ ~ ~ ~ ~