Representative mammalian neurotransmitters and the receptors mediating their effectsa.
| Class | Neurotransmitters | Receptorsb | |
|---|---|---|---|
| Ionotropicc (subunits) | GPCR (“metabotropic”) | ||
| Monoamines | Dopamine | NONE ESTABLISHEDe | D1, D2, D3, D4, D5 |
| Serotonin | 5-HT3A, 5-HT3B, 5-HT3C, 5-HT3D, 5-HT3E | 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT4, 5-HT5A, 5-HT5B, 5-HT6, 5-HT7 | |
| Noradrenaline/norepinephrine | NONE ESTABLISHEDe | α1A, α1B, α1D, α2A, α2B, α2C, β1, β2, β3 | |
| Histamine | NONE ESTABLISHEDe | H1, H2, H3, H4 | |
| Amino acid (excitatory) | Glutamate | NMDA, AMPA, or kainate, depending on the combination of these subunits: AMPA: GluA1, GluA2, GluA3, GluA4. NMDA: GluN1, GluN2A, GluN2B, GluN2C, GluN2D, GluN3A, GluN3B. Kainate: GluK1, GluK2, GluK3, GluK4, GluK5 | mGlu1, mGlu2, mGlu3, mGlu4, mGlu5, mGlu6, mGlu7, mGlu8 |
| Amino acid (inhibitory) | Gamma-aminobutyric acid (GABA) | GABAA (so far, 19 subunits have been reported: 6α, 3β, 3γ, 1δ, 1ε, 1π, 1θ and 3ρ) | GABAB1, GABAB2 |
| Glycine | α1–α4 and β subunits | GPRC6A, T1R2/T1R3 (sweet taste receptors), calcium-sensing receptord | |
| Choline | Acetylcholine | Nicotinic receptors (so far, 16 subunits have been reported: α1–α7, α9, α10, β1–β4, 1γ, 1δ, and 1ε) | M1, M2, M3, M4, M5 |
| Purines | ATP, UTP | P2X1, P2X2, P2X3, P2X4, P2X5, P2X6, P2X7 | P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, P2Y14 |
a: This table provides a representative, non-exhaustive overview; a comprehensive catalogue is beyond the scope of this Perspective. b: With the exception of the proposed metabotropic receptors listed for glycine, the source is the IUPHAR/BPS Guide to Pharmacology (https://www.guidetopharmacology.org/; accessed August 4, 2026). c: The ionotropic receptors listed are multimeric ligand-gated ion channels composed of identical or different subunits. d: Whether glycine acts as an agonist or as a modulator at the listed GPCRs remains debated. e: No receptors have been reported or accepted as belonging to this category. 5-HT: 5-hydroxytryptamine; AMPA: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; GPCRs: G protein-coupled receptors; NMDA: N-methyl-D-aspartate.