Recent evidence proposes that biologically active polypeptides are present in certain populations of neurons which also contain classical transmitters such as noradrenaline, acetylcholine, dopamine, and serotonin.
The concept of multiple synaptic messengers may explain how to magical process of brain functions. The diversity of localization of neurotransmitters throughout the brain implies a multiplicity of potential roles.
Classification of neurotransmitters as their main function in nervous system: excitatory and inhibitory
Excitatory neurotransmitters initiate neurons to start action potentials, an electrical signal, whereas inhibitory neurotransmitters inhibit action potentials being fired. Excitatory and inhibitory neurotransmitters should be balanced in brain and other organs.
Because, either lack of them can cause unwanted physiological conditions, or excessive synthesis of neurotransmitters may intolerable for our body 1.
Figure1:Biosynthetic pathway for the synthesis of dopamine, noradrenaline and adrenaline. (Abbreviations: TH, tyrosine hydroxylase; DDC, DOPA decarboxylase; D𝛽H, dopamine-𝛽-hydroxylase;PNMT – phenlyalanine–N–methyl transferase.)
Adrenaline, also called as epinephrine, is produced in high stress or being ready to unexpected situations.
This neurotransmitter provokes the increment of heart rate, cause contractilation of blood vessels, and dilates airways, to increase blood flow. All of these effects on body summarily tell us to sharp awareness 2.
Noradrenaline plays role in the frontal cortex, limbic areas of the brain, hypothalamus and the cerebellum are involved in the regulation of attention and cognition, mood and emotional behaviors as well as the sleep–wake cycle and eating behaviors.
Thus, deficiencies in NA will affect cortical, limbic, hypothalamic and brain stem regions that cause unwanted emotional and behavioral disorders 3.
Although noradrenaline has also been implicated in memory processes, preclinical and clinical trials with drugs that increase brain levels of these neurotransmitters have not been successful in improving learning and memory.
However, getting noradrenaline by natural ways that is produced from L-tyrosine 4; may give our body to decide for balancing of this crucial neurotransmitter.
Dopamine is another major neurotransmitter in central nervous system that is responsible for feelings of pleasure/satisfaction.
It is also associated with addiction, maintenance of normal physiological movement, and motivation/focusing.
The moods of satisfaction triggered by dopamine, and endurance of this emotion is related with repeated behaviors that lead to release of dopamine.
These behaviors generally could be natural, as with eating liked things or sexual activity.
Synthesis of dopamine in brain roots from L-tyrosine, so sufficient daily intake of L-tyrosine is needed for optimal dopamine level in nervous system 5.
Serotonin is one the best known neurotransmitter that thought to be a contributor to feelings of well-being and happiness 6.
It plays role in circadian rhythm, body’s awake and the sleep period, also regulates gastro intestinal movements, appetite and stomach activity.
Insufficient levels of serotonin is associated with depression, anxiety, and other mental complaints 7.
Exercise and regular sleep cycle can also have positive effects on the levels of serotonin 8.
References, Scientific citations
- Fields, H., Heinricher, M. & Mason, P. Neurotransmitters in nociceptive modulatory circuits. Annual review of neuroscience 14, 219 (1991).
- Brown, H., DiFrancesco, D. & Noble, S. How does adrenaline accelerate the heart? Nature 280, 235 (1979).
- Schwarz, L. A. et al. Viral-genetic tracing of the input–output organization of a central noradrenaline circuit. Nature 524, 88 (2015).
- Axelrod, J. Noradrenaline: fate and control of its biosynthesis. Science 173, 598-606 (1971).
- Aso, Y. & Rubin, G. M. Dopaminergic neurons write and update memories with cell-type-specific rules. Elife 5, e16135 (2016).
- Bogdanski, D. F., Pletscher, A., Brodie, B. B. & Udenfriend, S. Identification and assay of serotonin in brain. Journal of Pharmacology and Experimental Therapeutics 117, 82-88 (1956).
- Healy, D. Serotonin and depression. BMJ: British Medical Journal (Online) 350 (2015).
- O’Mahony, S. M., Clarke, G., Borre, Y., Dinan, T. & Cryan, J. Serotonin, tryptophan metabolism and the brain-gut-microbiome axis. Behavioural brain research 277, 32-48 (2015).