What are neurotransmitters?

There are millions and millions of molecules in the body, all important for different functions within the body. Whether it’s regulating digestive, bone, or heart function, a variety of different molecules are responsible for making sure processes at these locations are working properly. Although molecules regulating these functions are important, there aren’t many molecules that are more important than neurotransmitters. Neurotransmitters work to manage countless functions ranging from breathing and heart rate to learning and concentration [1]. The neurotransmitter network is also responsible for regulating psychological functions such as pain, fear, stress, and happiness [1]. But what exactly are these molecules? How do they work? What are the different types? Let’s keep going and answer all of those questions.

What exactly are neurotransmitters?

Neurotransmitters are the body’s chemical messengers that are released by nerve cells (neurons) in order to transmit messages between neurons [1] . Each neurotransmitter has a variety of specific psychological and physiological functions that it can affect, but all of them play a role in either activating or inhibiting certain functions within the body. These functions can range anywhere from increasing or decreasing stress levels, appetite, digestion, or muscle movement [2-4]. 

How do they work?

 Neurotransmitters are the way neurons are able to communicate with each other. Neurons are not connected to one another, so neurotransmitters are the neurons’ way of sending signals to one another across the small gap between cells known as the synapse. When a signal (action potential) reaches the end of a neuron near the synapse, it triggers the release of neurotransmitters out of the cell in small transport units called vesicles, where they reach a landing site known as a receptor on the receiving neuron [5]. Neurotransmitters are unique to the receptor they bind to, much like a lock and key system. When a specific neurotransmitter binds to its receptor site on the receiving neuron, it can either cause an excitatory or inhibitory effect [5]. An excitatory effect would cause the message to continue down the line of neurons, resulting in an increase in whatever function that neurotransmitter is in charge of regulating (increased heart rate, muscle contraction, etc.). An inhibitory effect would cause the message to stop being sent down the neuron, resulting in that function to be “turned off” or slowed down (slower breathing, reduced anxiety/stress, etc.). The process of neurons releasing neurotransmitters across synapses to receiving neurons in order to communicate a desired effect is known as neurotransmission [5]. Each neurotransmitter is in charge of its own unique set of psychological and physiological functions, and the increased or decreased release of these neurotransmitters is what causes changes in functions of the nervous system as well as bodily functions [1, 5]. There are dozens of known neurotransmitter molecules, and scientists are still discovering more about these small but essential molecules. 

Key Neurotransmitters

Acetylcholine

The first neurotransmitter molecule to be discovered, Acetylcholine is primarily an excitatory molecule that plays an important role in muscle movement. Acetylcholine is responsible for signaling our intention to move a muscle to muscle fibers in order to achieve that movement [2]. This neurotransmitter is also responsible for functions within the brain such as learning processing, concentration, and memory. As we get older, the concentrations of Acetylcholine begin to decrease, and these levels drop drastically in patients with Alzheimer’s disease [6].   

Dopamine

Dopamine is both an excitatory and inhibitory neurotransmitter, most popularly known as the pleasure or reward chemical [4]. Dopamine is released as a reward to a behavior in order to develop reward-relating learning patterns. Eating food, having sex, doing drugs, or achieving a desired task are all things that can stimulate the release of dopamine, resulting in a rush of positive emotions [4]. Because of this, dopamine can strongly influence motivation, decision making, learning, and working memory [4]. Dopamine is also responsible for other functions such as insulin release and voluntary muscle movements such as writing your name or driving a car [1]. 

Endorphins

Endorphins are inhibitory chemicals that are primarily responsible for reducing pain while boosting pleasure, making them natural pain relievers. Similar to dopamine, endorphins are released as a reward to a variety of different activities such as eating food or exercising [7]. Endorphins reduce stress and anxiety and increase pleasure in order to encourage us to do certain activities regardless of injury or stress. A common example of endorphins at work is the “runner's high”, or the elevated sense of pleasure a person feels when they run for an extended period of time [7]. This is due to an increase in endorphin release, in order to encourage a person to continue to do that activity. 

Serotonin

Serotonin is known as the mood chemical, responsible for stabilizing feelings such as happiness, anxiety, and depression [1, 8]. It also plays a role in regulating the sleep cycle by reducing anxiety and calming the body when serotonin levels are elevated [8]. Studies have shown that people suffering from chronic depression typically have lower levels of serotonin. Although popularly known for its mood modulating effects, serotonin also plays a big role in digestion. When toxic foods or substances enter the body, the release of serotonin causes an increase in nausea and controls bowel movements in order to help get rid of the toxic food or substance [8]. 

Glutamate

Glutamate is the most excitatory chemical within the cortex and hippocampus of the brain. It is primarily responsible for stimulating the release of other excitatory neurotransmitters and helps for fast signaling within the brain [9]. Due to its stimulating effect on other neurotransmitters such as acetylcholine, dopamine, and serotonin, it’s essential in the development and maintenance of cognitive functions, emotion, and motor control. Although the release of glutamate is important for these functions, too much glutamate causes excitotoxicity, resulting in the death of neurons and subsequent cognitive decline [3]. 

Gamma-aminobutyric acid (GABA)

Gamma-aminobutyric acid, also known as GABA, is the most inhibitory chemical that is the antagonist to glutamate, responsible for inhibiting the release of other neurotransmitters. GABA is thought to potentially be the first neurotransmitter active in the brain and has been shown to have an important role in early brain development [10]. The balance between GABA’s inhibitory regulation and glutamate’s excitatory regulation is essential for proper brain development and function. Because of this relationship, GABA has an important role in the process of learning and memory [10]. In the clinical setting, decreased levels of GABA have been associated with seizures and other neurological issues [1,10].

To sum it up –

Neurotransmitters are extremely important in regulating a wide variety of functions within the body. When it comes to brain health and function, having proper production and balance of neurotransmitters is essential. Healthy lifestyle habits such as proper nutrition, exercise, and supplementation can allow you to boost the production of these neurotransmitters, allowing for better cognitive function and mood support.

Written by David Levinson, BS Nutrition, NASM CPT and CES

References:

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4. Liu, C. and P.S. Kaeser, Mechanisms and regulation of dopamine release. Curr Opin Neurobiol, 2019. 57: p. 46-53.
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6. Rand, J., Acetylcholine. WormBook, 2007.
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