Welcome to 2 minute neuroscience, where I explain neuroscience topics in 2 minutes or
In this installment I will discuss glutamate.
Glutamate is an amino acid that also functions as a neurotransmitter.
Although glutamate is obtained through the diet, it cannot pass the blood-brain barrier
and thus must be synthesized in the brain.
It can be synthesized from alpha ketoglutarate, an intermediate product in the citric acid
Glutamate generally has excitatory actions, meaning that when it interacts with the receptors
of a neuron it makes that neuron more likely to fire an action potential.
It is, in fact, used at the vast majority of excitatory connections in the brain and
at more than half of all synapses in the brain.
Glutamate interacts with several different types of receptors.
There are 3 identified ionotropic glutamate receptors, named for substances that activate
them: NMDA, AMPA, and kainate receptors.
When activated, all 3 allow positively charged sodium ions to flow into a postsynaptic neuron,
depolarizing the neuron and making it more likely to fire an action potential.
NMDA receptors have unique characteristics that make them well-suited to be involved
in synaptic plasticity, or synaptic changes that occur in response to experience, which
are an important component of learning and memory.
There are also 3 identified types of metabotropic glutamate receptors.
These receptors have more varied effects than ionotropic glutamate receptors, and may be
involved with excitatory or inhibitory actions.
Glutamate is removed from the synaptic cleft by a class of transporter proteins called
the excitatory amino acid transporters, or EAATs.
EAATs carry glutamate into neurons and glial cells.
Glutamate taken into glial cells is converted to the amino acid glutamine by the enzyme
Glutamine is then transported back into neurons, where it is converted back to glutamate.
This process is referred to as the glutamate-glutamine cycle.