What makes a neuromodulator different from a fast transmitter like glutamate? · Grey Matter

Glutamate and GABA act through ion channels at a specific synapse for milliseconds, so they carry the content of a signal: which cell, when, and with what sign.

What makes a neuromodulator different from a fast transmitter like glutamate?

Glutamate and GABA act through ion channels at a specific synapse for milliseconds, so they carry the content of a signal: which cell, when, and with what sign. Neuromodulators such as dopamine, noradrenaline, serotonin and acetylcholine come from small nuclei with widely branching axons, are often released outside synapses, and act mostly through G protein-coupled receptors for seconds to minutes. They change how strongly neurons respond, how likely synapses are to release, and whether coincident activity will be stored. The same molecule can be both (acetylcholine is a fast transmitter at muscle and a modulator in the cortex), so the distinction is about the receptor and the wiring, more than the chemical.