Amino acid neurotransmitter
An amino acid neurotransmitter is an amino acid which is able to transmit a nerve message across a synapse. Neurotransmitters (chemicals) are packaged into vesicles that cluster beneath the axon terminal membrane on the presynaptic side of a synapse in a process called endocytosis.
Source: Wikipedia — Amino acid neurotransmitter (CC BY-SA 4.0)