The "Amine" transmitters are acetylcholine, serotonin (5-hydroxytryptamine),  and
the three catecholamine transmitters- dopamine, norepinephrine, and epinephrine. 
The catecholamine transmitters and serotonin have single primary amino groups,
and are sometimes  called "monoamines".  Acetylcholine has a quarternary amine
group, and so while it is an      "amine" it is not strictly speaking a
"monoamine".  A related transmitter, is histamine, which has two amine groups
(i.e., a di-amine). The amine transmitter are found in brain tissue
concentrations of nM/mg protein.