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GLUTAMATE

The main excitatory transmitter

Where Used at most excitatory synapses in the brain
Receptors Ionotropic AMPA, NMDA, and kainate receptors, plus metabotropic mGluRs
Role Fast signaling, and strengthening synapses during learning
Glutamate is the brain's go signal.

THE BALANCE

Two forces in tension

glutamate excites GABA inhibits too much: seizures too much: sedation Excitation and inhibition stay in balance Healthy circuits depend on the balance, not on either side alone

Neural circuits depend on a steady balance between excitation and inhibition.

Activity is a balance, not a quantity.

GABA

The main inhibitory transmitter

Made from Glutamate, using the enzyme glutamate decarboxylase (GAD)
GABA-A An ionotropic receptor that lets chloride flow in and quiets the cell
GABA-B A metabotropic receptor with slower, longer-lasting inhibition
The brain makes its brake from the same raw material as its accelerator.

WHEN IT SLIPS

Too much on either side

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Too much excitation

Can cause seizures. In stroke, glutamate overload damages neurons, which is called excitotoxicity

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Too much inhibition

Causes sedation. Benzodiazepines and alcohol enhance GABA-A activity

Many drugs work by tilting this balance.

WHY MEASURE THEM

Two transmitters, very different sensors

Glutamate and GABA are not easily oxidized at an electrode the way dopamine is, so they need other tools, such as enzyme-based electrodes or fluorescent protein sensors. You will meet these in Part 4.

Chemistry decides which sensor can see a molecule.

UNIT 6 STUDY COMPLETE

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Ready for the Fab Challenge?

You've learned how glutamate and GABA balance each other and what happens when the balance slips.