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Neurotransmitters are chemicals naturally produced in the body that facilitate communication between nerve cells in the brain and between nerve cells and the body.

There are no approved methods for determining the level of neurotransmitters in the brain.

In spite of numerous “labs” that offer “neurotransmitter panels,” such testing cannot measure uptake mechanisms, receptor site sensitivity, reuptake performance, type of receptor sites, degradation rates, agonist and antagonist influences from chemical messengers, hormone impact, or functional variables.

It was once believed hormones were only managed by the organs and neurotransmitters were only managed by the brain. Extensive research has illustrated that the endocrine and digestive systems and brain work together as an integrated system and hormones and neurotransmitters are produced in the brain and organs.

You should be skeptical of supplements advertised to affect neurotransmitters. Supplements are not regulated and may not have the listed level, if any, of the advertised active ingredient. In addition, ingesting a substance does not mean it will cross the blood-brain barrier.

Never take a neurotransmitter or amino acid supplement without medical supervision. Toxicity could occur. You could throw off the delicate balance between symbiotic amino acids. The public attitude toward supplements is that they “can’t hurt.” In fact, they can be fatal if taken in toxic quantities.

5-Hydroxytryptophan (5-HTP) is a naturally occurring amino acid and chemical precursor as well as a metabolic intermediate in the biosynthesis of the neurotransmitters serotonin and melatonin from tryptophan. It is decarboxylated to serotonin (5-hydroxytryptamine or 5-HT) by the enzyme aromatic-L-amino-acid decarboxylase with the help of vitamin B6. This reaction occurs both in nervous tissue and in the liver. 5-HTP crosses the blood–brain barrier, while 5-HT does not. Excess 5-HTP, especially when administered with Vitamin B6, is thought to be metabolized and excreted.

Acetylcholine governs muscle contractions and prompts glands to secrete hormones.  It acts on the peripheral nervous system (PNS), central nervous system (CNS), and the motor division of the somatic nervous system.

It can be a factor in  myasthenia gravis and Alzheimer’s. Drugs that affect acetylcholine receptor agonists and antagonists can either have an effect directly on the receptors or exert their effects indirectly by affecting the enzyme acetylcholinesterase, which degrades the receptor ligand. Agonists increase the level of receptor activation, antagonists reduce it. In cardiac tissue, acetylcholine neurotransmission has an inhibitory effect, which lowers heart rate. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle.

Catecholamines, Fractionated, 24-Hour Urine (without Creatinine) test includes dopamine, epinephrine/adrenaline, norepinephrine/noradrenaline, and total catecholamines (calculated). Catecholamines are more often measured with a urine test than with a blood test.

For more information on this test, visit Quest Labs.

Catecholamines, Fractionated, Plasma Includes dopamine, epinephrine, norepinephrine, and total catecholamines (calculated).

This test is used to screen for pheochromocytomas, neuroblastomas, ganglioneuromas, ganglioblastomas, severe stress, strenuous exercise, and acute anxiety.

For more information on this test, visit Quest Labs.

Dopamine has several distinct systems that play a role in mood, control of complex movement, and reward-motivated behavior.  In the blood vessels, it inhibits norepinephrine release and acts as a vasodilator. In the kidneys, it increases sodium excretion and urine output. In the pancreas, it reduces insulin production. In the digestive system, it reduces gastrointestinal motility and protects intestinal mucosa. In the immune system, it reduces the activity of lymphocytes. There are many drugs that affect dopamine levels and they are often highly addictive. Loss of dopamine production is a factor in Parkinson’s disease.

Epinephrine/Adrenaline is secreted by the medulla of the adrenal glands and produced at the ends of sympathetic nerve fibres, where they serve as chemical mediators for conveying the nerve impulses to effector organs. Epinephrine binds to a variety of adrenergic receptors and is a nonselective agonist of all adrenergic receptors, which triggers a number of metabolic changes.

Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis in the liver and muscle, and stimulates glycolysis in muscle. β-Adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue.

Together, these effects lead to increased blood glucose and fatty acids, providing substrates for energy production within cells throughout the body. Low, or absent, concentrations of epinephrine can be seen in autonomic neuropathy or following adrenalectomy.

Failure of the adrenal cortex, as with Addison’s disease, can suppress epinephrine secretion and depends on the high concentration of cortisol that drains from the cortex to the medulla. Drugs that effect epinephrine/adrenaline, both prescription and over the counter, are dangerous if taken in large quantities.

Gamma-aminobutyric acid (GABA), or γ-Aminobutyric acid, is the primary inhibitory neurotransmitter, helps control muscle activity, and is an important part of the visual system. It is utilized in the intestine, stomach, pancreas, Fallopian tube, uterus, ovary, testis, kidney, urinary bladder, lung, and liver.

Two general classes of GABA are GABA-α, in which the receptor is part of a ligand-gated ion channel complex, and GABA-β metabotropic receptors, which are G protein-coupled receptors that open or close ion channels via intermediaries (G proteins).

GABA is measured as part of the amino acid panel. Oral GABA does not cross the blood-brain barrier. There is no over-the-counter GABA alternative.

In many autoimmune diseases such as diabetes, myasthenia gravis, and stiff-person syndrome, antibodies attack the GAD65 and GAD67 enzymes that catalyze the production of GABA.

In spastic diplegia in humans, GABA absorption becomes impaired by nerves damaged from the condition's upper motor neuron lesion, which leads to hypertonia of the muscles signaled by those nerves that can no longer absorb GABA.

GABAergic drugs are used to treat stiff-person syndrome.

Norepinephrine/noradrenaline is secreted by the medulla of the adrenal glands. It is the hormone and neurotransmitter most responsible for vigilant concentration.  An increase in norepinephrine from the sympathetic nervous system increases the rate of contractions in the heart. As a stress hormone, norepinephrine affects parts of the brain, such as the amygdala, where attention and responses are controlled. Norepinephrine also underlies the fight-or-flight response, along with epinephrine, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing blood flow to skeletal muscle. It increases the brain's oxygen supply. There are many prescription drugs that affect norepinephrine.

Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter derived from tryptophan found primarily (90%) in the gastrointestinal tract (GI tract) where it regulates intestinal movement, platelets, and the central nervous system where it regulates mood, appetite, and sleep. It also impacts memory and learning. Serotonin is metabolized mainly to 5-HIAA, chiefly by the liver.

There are many serotonin-modulating drugs, such as serotonin-reuptake inhibitors used to treat depression.

The serum serotonin level is used to screen for carcinoid tumors, neuroendocrine tumors, pheocrhromocytoma, and small cell lung cancer.

For more information on these tests, visit Quest Labs.


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