NEUROTRANSMITTERS
Neurotransmitters
Measuring the concentration of biogene amines in platelets.
The test measures the level of biological amines or neurotransmitters in platelets. Measurement of blood platelet levels was chosen because these (relative to serum values) are relatively high and therefore relatively easy to measure and because the values are relatively stable and are not affected by acute increases in plasma under the influence of stress (for example caused by blood sampling). The measurement of the biological amines in the blood platelets is also preferable to that in urine because the concentration of (the free form of these substances) in the urine is partly determined by the acidity of the urine.
Biological amines in blood plates?
In this test the level of one or more of the following biological amines can be measured:
• Dopamine
• Epinephrine (Adrenaline)
• Norepinephrine (Noradrenaline)
• Normetanephrine
• Serotonin
• Metanephrine
BIOLOGICAL AMINES
Neurotransmitters are the transmitters of the nerve signals. They are released at the end (the presynapse) of one nerve, end up in the space between the nerves (the synapse fissure) and then exert a stimulating or inhibiting influence on the adjacent nerve (postsynap).
There are three classes of neurotransmitters - the biological amines, amino acids, and peptides. The biological amines include the three major catecholamines (norepinephrine, epinephrine and dopamine), an indolamine (serotonin), an ethylamine (histamine) and a quaternary amine (acethylcholine).
The catecholamines norepinephrine, epinephrine and dopamine are formed from the amino acid tyrosine via hydroxylation and decarboxylation. Part of the tyrosine is formed from the essential amino acid phenylalanine, but most comes from food. In a first step, tyrosine is hydroxylated to 3,4-dihydroxy-phenylalanin (DOPA). This step determines speed. The DOPA can be decarboxylated to dopamine, which in turn can be hydroxylated to norepinephrine. In the latter reaction, copper and vitamin C are needed as a co-factor. Epinephrine can be formed from norepinephrine via N-methylation.
Serotonin is formed from the essential amino acid tryptophan via hydroxylation and decarboxylation.
After their release into the space between the nerves and their action on the postsynaps, epinephrine and norepinephrine are converted into biologically inactive substances via oxidation and methylation. The oxidation is catalyzed by the enzyme monoamine oxidase (MAO) and the methylation by catechol-o-methyl transferase (COMT). Metanephrine and normetanephrine are metabolites from the inactivation of epinephrine and norepinephrine, respectively.
Dopamine is inactivated in a similar way to norepinephrine.
Released serotonin is first re-absorbed through an active mechanism and (subsequently) inactivated by MAO.The biological amine neurotransmitters are well known to most psychiatrists. They were the first neurotransmitters to be discovered, and research has been conducted into these substances for a relatively long time. The effect of many of the general drugs used in psychiatry is based on influencing one or more of the biological amines.
Fuction of biological amines and influences at their level?
The catecholamines (norepinehrine, epinephrine and dopamine) influence many functions. In most cases they are not the only regulators, but they work closely with hormones and other neuronal systems. This results in very fine regulation of body processes.
Dopamine and norepinephrine work as neurotransmitters in the brain and the autonomic nervous system. They are also formed in the adrenal glands. Outside the central nervous system, they have a regulatory role in carbohydrate and fat metabolism. They are stored in blisters in the adrenal glands and are released in response to a shock reaction, emotional stress, (strenuous physical) exertion, cold or a low level of glucose in the blood. Norepi-nephrine and epinephrine increase the breakdown of triacylglycerol and glycogen and increase the output of the heart and blood pressure.
The action of these substances is very related to that of the thyroid hormones. Both stimulate the (speed of) the metabolism and the nervous system and they have a similar effect on the cardiovascular system.
The level of catecholamines can be increased with the following conditions:
- Hypothyroidism (an underactive thyroid function)
- Diuretic therapy (fluid drift)
- High alcohol intake
- Hypoglycaemia (low blood sugar)
- Hypoxia (too low oxygen content)
- Severe acidosis (high acidity / low pH)
- Cushing's syndrome (disease caused by increased (e production of) cortisol.)
- Myocardial infarction
- Hemolytic anemia
- Essential hypotension
- Severe kidney diseases
- Lymphoma
- Decreased levels of catecholamines can be found at:
- Autism
- Attention disorders (ADD / ADHD)
- Specific developmental delays in childrenen
When is it meaningful to perform an catecholamines test?
Epinephrine in platelets
Epinephrine (adrenaline) is almost exclusively produced in the adrenal marrow. It works on the humoral part of the sympathetic nervous system. The measurement can provide valuable information for the following conditions:
Stressful situations, such as :
- Hypoglycaemia
- Essential high blood pressure
- Myocardial infarction
- Suspected adrenal tumor
- Neuroblastoma
- Progressive muscular dystrophy and myasthenia Gravis
- Physical exhaustion
- Hypothyroidism, diuretic therapy and Cushing's syndrome
Norepinephrine in platelets
Norepinephrine (noradrenaline) is made at the ends of sympathetic nerves.
The measurement can provide valuable information in the event of:
- Malfunction of the baroreceptor reflexes (the receptors that are stimulated by changes in blood pressure and that lie in the blood vessel wall)
- High blood pressure due to pheochromocytoma (a tumor of adrenal marrow chromaffin tissue).
- Various problems with the functioning of autonomic nerves.
Dopamine in platelets
Dopamine is released from peripheral sympathetic nerve endings and from the adrenal glands.
The measurement can provide valuable information in the following (mainly chronic) situations.
- Stress-related hypotension
- Orthostatic hypotension (low blood pressure when getting up quickly)
- Seizures with hypotension
- Reduced ejaculation
- Abundant urination at night
- Abnormalities in the T-wave (EGG)
- Schizophrenia
- Behavioral changes related to mania and depression
- Hypomagnesemia (low blood magnesium)
- Tardive dyskinesia (stereotype movements occurring later in life)
- Parkinson's symptoms.
Serotonin in platelets
Serotonin is formed in the chromaffin cells of the intestine, and by nerve cells of the central and peripheral nervous system.
- Cystic fibrosis
- Ovarian cancer
- Local sprue
- Severe skeletal pain or sciatica
- Spasms of smooth muscles
- Bronchial adenoma
- Poor intake of the food
- Celiac diseases
- Whipple disease
- Stasis syndrome
- Chronic bowel obstruction
- Oat cell cancer of the respiratory system
- Long-term nutritional hypoglycaemia
- long-term insomnia
- Problems with MAO synthesis or excretion
- Malignant stomach lymphoma
- Highlighted manic phase of bipolar depression
Serotonin in platelets
reduced level can be an indication of:
- reduced level can be an indication of:
- Depression
- Small intestine resection
- Phenyl ketonuria
- Hartnup disease
- Mastocytosis
Serotonin in platelets
Very high values can be an indication of:
- Lial tumor
- Pancreatic tumor
- Duodenal tumor
- Galt tumor
- Large malignant tumor
Clinical alert
With the aid of platelets serotonin, tumors can be discovered that are missed in the determination of serotonin in urine or the HIAA assay.
Catecholamines and related biological amines is recommended also for the following conditions:
- Fatigue
- Overactivity
- Stress
- Mental / psychological problems
- Depression
- High / low blood pressure
- Fast / slow metabolism
- Heart and vascular disease
- Parkinson's