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Monoamine neurotransmitters are neurotransmitters and neuromodulators that contain one amino group that is connected to an aromatic ring by a two-carbon chain (-CH2-CH2-). All monoamines are derived from aromatic amino acids like phenylalanine, tyrosine, tryptophan, and the thyroid hormones by the action of aromatic amino acid decarboxylase enzymes. Monoaminergic systems, i.e., the networks of neurons that utilize monoamine neurotransmitters, are involved in the regulation of cognitive processes such as emotion, arousal, and certain types of memory. It has been found that monoamine neurotransmitters play an important role in the secretion and production of neurotrophin-3 by astrocytes, a chemical which maintains neuron integrity and provides neurons with trophic support. Drugs used to increase (or reduce) the effect of monoamine are sometimes used to treat patients with psychiatric disorders, including depression, anxiety, and schizophrenia.
Contents
Examples
Specific transporter proteins called monoamine transporters that transport monoamines in or out of a cell exist. These are the dopamine transporter (DAT), serotonin transporter (SERT), and the norepinephrine transporter (NET) in the outer cell membrane and the vesicular monoamine transporter (VMAT1 and VMAT2) in the membrane of intracellular vesicles.
After release into the synaptic cleft, monoamine neurotransmitter action is ended by reuptake into the presynaptic terminal. There, they can be repackaged into synaptic vesicles or degraded by the enzyme monoamine oxidase (MAO), which is a target of monoamine oxidase inhibitors, a class of antidepressants.
Evolution
As demonstrated by the wide existence of monoamine transmitters, an organism's ability to modify its behavior is advantageous to its survival. This system is found in various species such as nematodes, lobsters, desert locusts, hens, mice and zebra finches.
Disorders
Disorders of monoamine neurotransmitters exist, part of a growing number of neurotransmitter disorders identified. Such disorders are responsible for biosynthesis degradation and difficulty in transporting neurotransmitters such as dopamine, norepinephrine, epinephrine, or serotonin. Monoamine neurotransmitter disorders mimic the symptoms of other more prevalent neurological disorders (e.g. cerebral palsy) and thus are frequently misdiagnosed.