Definition and Criteria

Neurotransmitters are endogenous chemical messengers that allow neurons to communicate with one another, as well as with muscles and glands. To be classified as a neurotransmitter, a chemical must be synthesized within the neuron, released into the synaptic cleft upon electrical stimulation, and possess a specific mechanism for inactivation or removal.

Classification and Function

Neurotransmitters are broadly categorized by their chemical structure and their effect on the postsynaptic cell:

• Amino Acids: These mediate fast signaling. Glutamate is the primary excitatory neurotransmitter in the brain, while GABA (γ-aminobutyric acid) and Glycine are the main inhibitory neurotransmitters.

• Biogenic Amines (Monoamines): These play critical roles in regulating mood, attention, and motor  ...