All about neurotransmitters
Neurotransmitters are the messenger chemicals in our brains that transmit signals between brain cells. Some well-known neurotransmitters include melatonin and endorphins. But what exactly are neurotransmitters, and what do they have to do with our gut? We’ll take you through it.
What are neurotransmitters?
Neurotransmitters are signalling chemicals in the brain, also known as messenger substances. They’re called this because they facilitate communication between different brain cells (neurones)—around one hundred thousand signals per second. Neurotransmitters are involved in several parts of our nervous system:
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The parasympathetic nervous system: this part is responsible for the body’s resting state (rest & digest).
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The sympathetic nervous system: this part is responsible for the body’s action state (fight or flight).
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The enteric nervous system: this is the nervous system of our digestive tract.
Neurotransmitters play a crucial role in how we think, feel and behave. That’s why it’s so important for your neurotransmitters to be in balance. When there’s an imbalance in neurotransmitters, it can affect various processes in the brain.
Which neurotransmitters are there?
Neurotransmitters can be divided into four categories: amino acids, monoamines, peptides and others. There are more than a hundred neurotransmitters in total, but the best known are:
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Glutamate: glutamate is involved in memory and learning.
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GABA: GABA is involved in reducing pain and stress, and in relaxation and calm.
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Serotonin: serotonin is involved in mood, sleep, appetite and regulating bowel movements. As the ‘happiness hormone’, it also plays a role in promoting feelings of wellbeing and happiness.
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Dopamine: dopamine is involved in motivation, reward and pleasure.
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Melatonin: melatonin is involved in regulating the sleep–wake cycle.
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Noradrenaline: noradrenaline is involved in regulating alertness, attention and the stress response.
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Acetylcholine: acetylcholine plays a role in memory, attention and cognitive functions.
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Endorphins: endorphins are involved in regulating pain and promoting pleasure. They’re also associated with the “runner’s high” and play a role in reducing stress and promoting relaxation.
Neurotransmitters and the gut
Did you know that some neurotransmitters are (partly) produced in the gut? This happens in the enteric nervous system: a complex network of nerve cells and neurotransmitters in the intestines. Some of the most important neurotransmitters produced in the gut are serotonin, acetylcholine, GABA and dopamine. (source)
Excitatory and inhibitory neurotransmitters
A neurotransmitter always has one of two tasks: activating (exciting) or slowing down (inhibiting) activity in a particular cell. Below you can see which neurotransmitters are excitatory and inhibitory, and which category they fall into.
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Neurotransmitter
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Type
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Category
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Glutamate
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Excitatory
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Amino acid
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GABA
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Inhibitory
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Amino acid
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Serotonin
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Inhibitory
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Monoamine
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Dopamine
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Excitatory/Inhibitory
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Monoamine
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Noradrenaline
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Excitatory
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Monoamine
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Acetylcholine
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Excitatory/Inhibitory
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Other (choline derivative)
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Endorphins
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Inhibitory
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Peptide
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Melatonin
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Inhibitory
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Other (melatonin)
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Some neurotransmitters can be both excitatory and inhibitory in nature. This depends on the receiving cell (receptor) they bind to and the brain region in which they act. Examples include dopamine and acetylcholine. Below is a brief explanation of what the effect can be, depending on where the neurotransmitter binds.
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Neurotransmitter
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Excitatory effect
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Inhibitory effect
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Dopamine
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Binds to dopamine D1 receptors and increases neural activity, which can lead to feelings of reward, motivation and stimulation.
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Binds to dopamine D2 receptors and reduces neural activity, which may be involved in regulating motor function and controlling impulsive behaviour.
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Acetylcholine
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Binds to muscle cells at the neuromuscular junction and causes muscle contraction, which is involved in voluntary movement of the body.
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Binds to receptors in the basal ganglia and regulates neurone activity, which is important for functions such as movement control, cognition and memory.
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* Please note that this is a simplified representation of the effects of dopamine and acetylcholine, and that there is greater complexity and nuance in how these neurotransmitters work across different brain areas and contexts.
