Answer
There are more than 100 neurotransmitters of several chemical types. Some of these retard the firing of action potentials (AP); these are termed inhibitory neurotransmitters. Excitatory neurotransmitters are NTs that facilitate the triggering of APs.
Work Step by Step
The major excitatory NTs are acetylcholine(ACH), glutamate, aspartate, and nitric oxide (NO). Substance P. histamine, norepinephrine, and epinephrine are also excitatory. Glycine, gamma-aminobutyric acid (GABA), and tryptophan are well-known inhibitory neurotransmitters. Serotonin, and Beta-endorphins are usually included in this latter group. Some NTs that have both excitatory and inhibitory effects ( dependent mainly on receptors) are acetylcholine and dopamine.
