There are three main categories of neurotransmitters in the brain:
Small molecules used for fast-action excitatory / inhibitory information transmission (glutamate, GABA)
Small molecules used for slower modulation of network activity (dopamine,serotonin, and 3 others)
Peptides (large protein molecules) used for even slower modulation of circuit function (endorphins, cannabinoids, oxytocin, many others)
GABA
Below are the main neurotransmitters in the brain organized by functional role, along with their short abbreviation, their approximate role, and the letter code used for their associated neuroreceptors. For example, the neurotransmitter “dopamine” is abbreviated “DA” and its receptors have names like D1, D2, D3, D4, and D5.
Small molecule – signal transmission:
glutamate (Glu) – excitatory, receptors are AMPA, NMDA, kainate, mGluR
GABA – inhibitory, receptors are “GABA”
Small molecule – neuromodulators:
dopamine (DA) – behavior learning, receptors are “D”
serotonin (5-HT) – mood(?), receptors are “5-HT”
acetylcholine (ACh) – attention, receptors are “M” and nicotinic
norepinephrine (NE) – vigilance, receptors are alpha, beta
histamine (HIST) – sleep/wake, receptors are “H”
Small molecule – other:
epinephrine/adrenalin (EP/AD) – receptors are alpha, beta
melotonin (MEL) – circadian rhythm, receptors are “M”
adenosine – receptors are “A” (caffeine affects these)
nitric oxide (NO)
glycine – inhibitory, receptors are “Gly”, used only in spinal cord
Peptide (large molecule):
Oxytocin
endorphins (enkephalin, dynorphin) – receptors are mu, sigma, and kappa (morphine, codeine, heroine, etc. affect these)
cannabinoids – receptors are “CB” (marijuana affects these)
oxytocin – the “love” neurotransmitter (pair-bonding)
orexin / hypocretin – regulation of sleep/wake cycle, receptors are “OX”, (dysfunction causes narcolepsy)
corticotropin releasing factor (CRF) – regulation of stress response
Neuroscientist Paul King weighs in via Quora:
