Many people know the term neurotransmitters and can even name one or two of them. However, that is where the knowledge ends.
It’s highly beneficial to know about each neurotransmitter and what they do for your brain and body.
Neurotransmitters can help us stay calm, improve learning and memory, give us steady energy, manage pain, boost mood, regulate appetite, promote healthy sleep cycles, and contribute to overall health and well-being.
So what exactly are neurotransmitters, and how do they work?
- What is a Neurotransmitter?
- How Do Neurotransmitters Work?
- Classification By Function
- Types of Neurotransmitters
- Disorders Associated With Neurotransmitters
What is a Neurotransmitter?
Neurotransmitters exist as the body’s chemical messengers that communicate with each other and with target tissues through synaptic transmission or neurotransmission.
Overall, over 40 neurotransmitters exist within the human central nervous system (CNS), each having a specific and vital function for human behavior.
However, scientists still don’t know exactly how many neurotransmitters in total are in the human brain.
Neurotransmitters are synthesized and released from the nerve ending into the synaptic cleft, and then they bind to receptor proteins in the cellular membrane of the target tissue.
In addition, small-molecule transmitters do most of the work and include GABA, acetylcholine, dopamine, and more.
According to neuroscience, there are three different types of neurotransmitters identified depending on the action of the target cells.
How the neurotransmitter affects the target cell determines whether it is a modulating, excitatory, or inhibitory neurotransmitter (1).
How Do Neurotransmitters Work?
For neurons to work appropriately and effectively send messages throughout the body, they need something to traverse the gap between them.
This gap, called a synapse, requires neurotransmission or electrical impulse for proper chemical transmission between the presynaptic neuron, chemical messenger, and the postsynaptic neuron that receives the messages.
Usually, the neurotransmitter molecules will be released from the axon terminal after an action potential reaches the synapse.
When the electrical signal reaches the end of a neuron, it will trigger the release of neurotransmitters via tiny sacs called synaptic vesicles. Then, the neurotransmitters can cross the small gap to other cells that contain receptors.
The neurotransmitter can then bind to the specific receptors that can cause changes in the target cells. This is where the neurotransmitter will have exciting, inhibiting, or modulatory action.
The neurotransmitter acts as a critical role, and the receptor acts as a lock. Each of the different neurotransmitters may only act on the specific neurotransmitters that it fits into.
After the neurotransmitters play their role, the activity can be stopped through a precise mechanism. The mechanisms include:
- Degradation is when an enzyme changes the structure of the neurotransmitter so that it no longer fits the receptor.
- Diffusion is when the neurotransmitter begins to diffuse or drift away from the receptor.
- Reuptake is when the entire neurotransmitter molecule is taken back by the neuron’s axon, which initially releases neurotransmitters.
Classification By Function
Researchers categorize neurotransmitters by their brain and bodily functions. While neurotransmitters offer many necessary functions, they will align with these three classifications:
- Excitatory neurotransmitters
- Inhibitory neurotransmitters
- Modulatory neurotransmitters
In addition, some other neurotransmitters play a role in both excitatory and inhibitory actions.
Excitatory neurotransmitters have an excitatory effect, making it more likely for the neuron to fire an action potential.
The excitatory process of neurotransmission can influence energy and mood in some cases, like epinephrine.
This type of neurotransmitter will have inhibitory effects on the neuron. When they inhibit the neuron, it will be less likely to fire an action potential.
Major inhibitory neurotransmitters include serotonin and gamma-aminobutyric (GABA).
Modulatory neurotransmitters, also known as neuromodulators, will influence other chemical messengers and affect numerous neurons simultaneously.
When the axon terminals release neurotransmitters with modulatory properties, they immediately impact receptor site neurons.
Types of Neurotransmitters
In addition to the different classifications based on how they interact, different chemicals work as neurotransmitters.
Amino acid neurotransmitters are organic compounds made of amino and carboxylate that can transfer nerve impulses across the synaptic gap.
They reside in vesicles and axons in the terminal membrane on the presynaptic cell side of the synapse, known as endocytosis.
Two amino acids that can transmit signals to the postsynaptic cell are GABA and Glutamate.
Gamma-aminobutyric Acid (GABA)
Gamma-aminobutyric acid (GABA) is a naturally occurring amino acid in the hippocampus that has the ability to inhibit neurons from regulating and supporting a variety of natural processes.
GABA contributes to motor control and vision. However, the most exciting property of GABA is that it can offer a calming effect and may be used for relaxation and the treatment of anxiety disorders.
While many supplements include GABA, it’s better to use a precursor to GABA that readily crosses the blood-brain barrier if you want to treat anxiety (2).
In addition, some anti-anxiety medications, like benzodiazepines, work by affecting GABA within the brain. This reduces anxious feelings rapidly and can halt a panic attack.
Glutamate is the most common neurotransmitter in the frontal cortex, and it plays a significant part in cognitive functions, including learning and memory.
However, too much glutamate can cause excitotoxicity, which can cause cell death and is associated with Alzheimer’s disease, stroke, epileptic seizures, and other traumatic brain injuries and illnesses.
Proper levels of glutamate are believed to help with memory formation and may reverse memory loss, mainly when it is associated with advanced aging.
However, more studies are needed to confirm these benefits. Finally, scientists have also shown that glutamate controls breathing.
Neuropeptides are hormones that can carry signals through neurotransmission. A neuropeptide is a small protein produced by neurons that act on G protein-coupled receptors.
These neurons allow neuropeptides, like endorphins and oxytocin, to modulate through signals in the synapses and coexist in single neurons.
Oxytocin is a neuropeptide that acts as both hormone and neurotransmitter in the human brain.
The hypothalamus produces oxytocin that plays an essential role in bonding, social recognition, sexual reproduction, and managing the stress hormone cortisol.
Close social contact and connection trigger its release. It is also associated with trust and empathy and is released during loving relationships with other people. In fact, synthetic oxytocin is also used in labor and delivery.
Endorphins can inhibit pain signals and can also provide you with a feeling of euphoria.
Generally, endorphins are produced when we are in pain, and the most known example is “runner’s high” during aerobic exercise, but they can even release when you eat spicy food and laugh (3).
Endorphin deficiency may even play a role in fibromyalgia. Additionally, endorphins work similarly to opioids by fighting pain and causing waves of euphoric relaxation.
In some cases, endorphins can send messages to act as a sedative on the system.
A monoamine contains one amino group connected to an aromatic ring by a two-carbon chain.
They are responsible for various bodily functions and signal neurons in the control of psychomotor, cardiovascular, respiratory, and gastrointestinal tract.
Because of this, some of the most crucial neurotransmitter signalings occur with monoamines like epinephrine, dopamine, and serotonin.
Epinephrine is another name for adrenaline, and it is a hormone and excitatory neurotransmitter released by the adrenal glands.
It is released as part of the fight-or-flight response as a reaction to stress or fear. These chemicals stimulate nerves and can even lead to insomnia if there is too high a concentration.
Epinephrine increases heart rate, supplies energy to the muscles, and may even help with prolonged concentration.
However, too much can also cause side effects like high blood pressure, diabetes, excessive stress, and heart disease.
Norepinephrine, or noradrenaline, plays a role in the flight or fight response and impacts alertness levels.
It supports quick action and is designed to spring your body and mind into action during dangerous or stressful situations.
Norepinephrine is also used as a prescription medication to treat low blood pressure and heart failure. However, low norepinephrine has also been tied to psychiatric conditions and physical ailments.
Histamine is a naturally occurring compound that works as a neurotransmitter in the brain and spinal cord.
It is most closely tied to allergic reactions because it is a component of the immune system and the way it responds to pathogens and other allergens.
A histamine reaction to an outside contaminant often causes red spots, itchiness, and other symptoms associated with allergies.
Antihistamine medications, like Benadryl, are the most common allergy medicines and work to relieve symptoms associated with high amounts of histamine.
Dopamine is the pleasure neurotransmitter because the release often occurs when we receive a reward for behavior. A reward could be food, sex, drugs, candy, or a plethora of other things.
In addition, dopamine levels are involved in motivation, decision-making, attention, working memory, learning, and movement. Dopamine also aids in planning and organization skills.
Research suggests that dopamine plays a vital role in Parkinson’s disease, addiction, schizophrenia, and other neuropsychiatric disorders (4).
Finally, many addictive drugs, like cocaine, are dopaminergic, which influence dopamine receptors because high levels can provide a sense of pleasure and euphoria.
Serotonin, or 5HT, is essential for mood, sleep, anxiety, sexuality, appetite, and more. Conversely, low serotonin levels in the brain are linked to depression, other mood disorders, and mental health conditions.
Some illicit drugs release serotonin or can affect serotonin receptors and cause euphoria. Also, some antidepressant medications can balance serotonin by blocking the reuptake of serotonin in the brain.
In turn, serotonin binds and plays a part in improving mood and reducing anxiety. In addition, serotonin is linked to reward and stimulates brain function.
Adequate serotonin levels in the brain can affect learning, memory, overall cognition, and a variety of psychological functions.
Purines are heterocyclic aromatic compounds that can send a direct signal to modulate the nervous system and cardiovascular function.
While they may not seem as prominent as things like dopamine, they still act within nerve cells to control the brain’s response to various situations in everyday life.
Adenosine is a naturally occurring neuromodulator that is involved in some essential brain processes.
For example, it can suppress arousal, thereby improving sleep and making it easier to relax during times where there are low levels of stress.
Adenosine Triphosphate (ATP)
Adenosine triphosphate, or ATP, is a neurotransmitter that acts in the central nervous system and peripheral nervous system.
It plays a role in autonomic control, sensory transduction, and communication with glial cells.
While further research is needed, researchers have shown that it can play a part in neurological issues like pain, trauma, and neurodegenerative disorders (5).
These are substances in gaseous form that move through synapses as well as in and out neighboring cells in the respiratory system and other components in the body.
As gas molecules, they are not stored long-term but often enter and exit through breathing activation and help to regulate normal responses by binding to ions.
This substance plays a significant role in affecting smooth muscle movements and muscle contractions.
It allows the muscles to relax and dilates blood vessels. This increases blood flow around the body that can help with strength and muscle tissue health and regular body movements.
Carbon monoxide is a potentially life-threatening gas chemical that is produced naturally by humans.
It acts as a neurotransmitter that can help to modulate the inflammatory response. Therefore, as long as it is not at dangerously high levels, it can fight inflammation, which can be wholly positive (6).
Acetylcholine is different from other neurotransmitters and acts as an excitatory neurotransmitter in the neuromuscular junction in skeletal muscle but is inhibitory in the heart.
Acetylcholine, also called ACh, was the first neurotransmitter discovered. It is a direct small molecule that primarily influences muscles and helps turn our intentions into actions passed from motor neurons to muscle fiber for muscle contraction.
Acetylcholine also plays a role in attention and neuroplasticity within the cortex and hippocampus.
Research also shows that low levels are associated with poor memory and learning and may even play a critical role in developing Alzheimer’s disease (7).
There is evidence that acetylcholine may also improve signaling from the presynaptic neuron to the receiving neuron. This effect on these two neurons may have positive outcomes related to cognition.
Disorders Associated With Neurotransmitters
When there is an imbalance in neurochemicals, it can cause problems. For example, sometimes other neurons may not produce enough of a neurotransmitter, or the neurotransmitter may be reabsorbed too quickly.
Occasionally the body may release neurotransmitters too fast or also release too much. These problems can lead to a variety of adverse effects.
Alzheimer’s, epilepsy, and Parkinson’s disease are all associated with deficits in critical neurotransmitters.
Researchers also recognize that neurotransmitters can have an impact on mental health. Because of this, many treatment options for posttraumatic stress disorder, depression, anxiety, and more are developed with this in mind.
Selective serotonin reuptake inhibitors (SSRIs) are some of the most popular antidepressant medications, and SSRIs work by increasing serotonin levels in the brain.
Another type called tricyclic antidepressants works by increasing serotonin and norepinephrine but blocking acetylcholine at the same time. Both options for depression work best when combined with therapy and other treatment options.
Neuroscience shows us that inadequate dopamine may also be involved with some health disorders and diseases, including schizophrenia, ADHD, and addiction. Not only that, but too little dopamine may also cause gastrointestinal and muscular problems.
Neurotransmitters can have a tremendous impact on our body and brain functions.
Probably, we will have good cognition, mood, and impulses when we have the proper level of neurotransmitters in the brain like dopamine, acetylcholine, serotonin, and more.
However, not everyone has enough of the chemicals responsible for these implications.
Sometimes, it takes medications or supplements to enhance or simulate certain neurotransmitters crucial in regulating cognitive and bodily functions.
A variety of factors can influence these neurochemicals and, while the regulation is complicated, the solution for increasing a naturally occurring chemical may be simpler than you realize.