Neurotransmitters are endogenous chemical messengers that transmit signals across a chemical synapses. These include neuromuscular junctions, the space between one neuron and another, between muscle cells, gland cells, and immune cells.
Over 100 substances that act as neurotransmitters to have been identified. The most common are:
- Amino acids: glutamate, aspartate, D-serine, γ-aminobutyric acid (GABA), glycine
- Gasotransmitters: nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S)
- Monoamines: dopamine (DA), norepinephrine (noradrenaline; NE, NA), epinephrine (adrenaline), histamine, serotonin (SER, 5-HT)
- Trace amines: phenethylamine, N-methylphenethylamine, tyramine, 3-iodothyronamine, octopamine, tryptamine, etc.
- Peptides: somatostatin, substance P, cocaine and amphetamine regulated transcript, opioid peptides
- Purines: adenosine triphosphate (ATP), adenosine
- Others: acetylcholine (ACh), anandamide, etc.
Endogenous - Growing or originating from within an organism.