Glutamate

What is glutamate?

Glutamate is a neurotransmitter. Neurotransmitters are “chemical messengers.” Their job is to send messages between nerve cells (neurons) in your brain.

In your brain, glutamate is the most abundant excitatory neurotransmitter. An excitatory neurotransmitter excites or stimulates a nerve cell, making it more likely that the chemical message will continue to move from nerve cell to nerve cell and not be stopped. Glutamate is essential for proper brain function.

Glutamate is recycled and made by glial cells in your brain. Glial cells convert “used” glutamate to glutamine, which is converted back again into glutamate when delivered back to the terminal area of nerve cells.

Glutamate is also needed for making another neurotransmitter in your brain called gamma-aminobutyric acid (GABA). GABA is known as the “calming” neurotransmitter. It’s involved in sleep, relaxation, anxiety regulation and muscle function.

Glutamate is also an amino acid. Amino acids are the building blocks of protein. Glutamate is your body’s most abundant amino acid. Glutamate in your body is made and stored in muscle tissue.

Glutamate is perhaps best known as the food additive monosodium glutamate (MSG).

How does glutamate work?

Neurotransmitters, like glutamate, are made by nerve cells and are stored in thin-walled vesicles called synaptic vesicles located at the axon terminal, which is at the end of each nerve cell. Each vesicle can contain thousands of neurotransmitter molecules.

As a message or signal travels along a nerve cell, the electrical charge of the signal causes the vesicles of neurotransmitters — in this case, glutamate — to be released into a fluid-filled space that’s between nerve cells. This space is called a synapse. On the other side of the synapse is the next nerve cell. Glutamate must bind to specific message-receiving receptors on this next nerve cell. After binding, glutamate then triggers a change or action in this next nerve cell and the communication signal continues on its way from nerve cell to nerve cell.

Unlike other neurotransmitters, glutamate can bind to four different receptors (like a master key that can fit into and work four different partner locks). This allows glutamate to have a major presence and ability to stimulate and communicate with other nerve cells. Glutamate is involved in more than 90% of all excitatory functions in the human brain.

In your brain, groups of nerve cells connect to form smaller circuits (to manage smaller tasks like memory retrieval) or larger, more extensive networks (to carry out larger more complex tasks, such as sight, hearing or movement). Glutamate is the most abundant neurotransmitter that carries the chemical message across these circuits and networks. How glutamate acts at the synapse between nerve cells can either strengthen or weaken the communication signal between these cells, which then affects the function to be carried out. Less than the right amount of glutamate released at the right places for the right amount of time results in poor communication. Too much glutamate can damage nerve cells and the communication network.

What does glutamate do in your body?

Glutamate’s functions include:

• Learning and memory. By interacting with four different receptors, glutamate has more opportunities to continue to have messages successfully and quickly sent between nerve cells. This fast signaling and information processing is an important aspect of learning and memory. Glutamate also allows nerve cells to build associated information, which is a foundation of memory.
• Energy source for brain cells. Glutamate can be used as an energy source when glucose levels — the main source of energy — are low.
• Chemical messenger. Glutamate allows chemical messages to be sent between nerve cells.
• Sleep-wake cycle manager. According to animal studies, glutamate levels are high when you’re awake and during the rapid eye movement (REM) phase of sleep.
• Pain signaler. Higher levels of glutamate are associated with an increase in pain levels.

How does your brain end up with too much glutamate?

Ways that too much glutamate can be in your brain include:

• Too much glutamate is released by nerve cells.
• Glutamate, directly released from glial cells in your brain, adds to the total amount in your brain.
• Excess glutamate remains in the space between nerve cells (the synapse), which can lead to too many glutamate receptors being continuously activated and nerve cells being continuously excited.
• Nerve cell receptors have become oversensitive to glutamate, meaning that fewer glutamate molecules are needed to excite them.

What happens when you have too much glutamate?

Too much glutamate in the brain can cause nerve cells to become overexcited. Overexcitement can lead to brain cell damage and/or death. In this case, glutamate is called an excitotoxin.

Having too much glutamate in the brain is associated with some conditions, including:

• Amyotrophic lateral sclerosis (Lou Gehrig’s disease).
• Multiple sclerosis.
• Alzheimer’s disease.
• Parkinson’s disease.
• Huntington’s disease.
• Stroke.
• Fibromyalgia.
• Chronic fatigue syndrome.

Mental health conditions that are thought to happen from problems with making or using glutamate include:

• Mood and anxiety disorders.
• Autism.
• Depression.
• Obsessive-compulsive disorder.
• Schizophrenia.

What happens when you have too little glutamate?

Too little glutamate in the brain is thought to result in:

• Trouble concentrating.
• Mental exhaustion.
• Insomnia.
• Low energy.

A note from Cleveland Clinic

Glutamate is the most abundant excitatory neurotransmitter in your brain and central nervous system. It’s needed to keep your brain functioning properly. Glutamate plays a major role in shaping learning and memory. Glutamate needs to be present at the right concentrations in the right places at the right time. Too much glutamate in your brain, in the wrong place, in too high of a concentration and for too long can cause brain cell damage or death. Some neurodegenerative diseases associated with having too much glutamate exciting nerve cells include Parkinson’s disease, Alzheimer’s disease and Huntington’s disease. Problems in making or using glutamate have been linked to mental health disorders including autism, depression and schizophrenia.