• Small: Amino acids (Arg) Arginine α2-Adrenergic receptors, imidazoline receptors NMDA receptors

Small: Amino acids Aspartate Asp – NMDA receptors

• Small: Amino acids Glutamate Glu Metabotropic glutamate receptors NMDA receptors, kainate receptors, AMPARs
• Small: Amino acids Gamma-aminobutyric acid GABA GABAB receptors GABAA receptors, GABAA-ρ receptors
• Small: Amino acids Glycine Gly – NMDA receptors, glycine receptors
• Small: Amino acids D-serine Ser – NMDA receptors
• Small: Acetylcholine Acetylcholine Ach Muscarinic acetylcholine receptors Nicotinic acetylcholine receptors
• Small: Monoamine (Phe/Tyr) Dopamine DA Dopamine receptors, trace amine-associated receptor 1[14][15] –
• Small: Monoamine (Phe/Tyr) Norepinephrine (noradrenaline) NE, NAd Adrenergic receptors –
• Small: Monoamine (Phe/Tyr) Epinephrine (adrenaline) Epi, Ad Adrenergic receptors –
• Small: Monoamine (Trp) Serotonin (5-hydroxytryptamine) 5-HT Serotonin receptors (all except 5-HT3) 5-HT3
• Small: Monoamine (His) Histamine H Histamine receptors –
• Small: Trace amine (Phe) Phenethylamine PEA Human trace amine-associated receptors: hTAAR1, hTAAR2 –
• Small: Trace amine (Phe) N-methylphenethylamine NMPEA hTAAR1 |*Small: Trace amine (Phe/Tyr) Tyramine TYR hTAAR1, hTAAR2 –
• Small: Trace amine (Phe/Tyr) octopamine Oct hTAAR1 –
• Small: Trace amine (Phe/Tyr) Synephrine Syn hTAAR1 –
• Small: Trace amine (Trp) Tryptamine hTAAR1, various serotonin receptors –
• Small: Trace amine (Trp) N-methyltryptamine NMT hTAAR1, various serotonin receptors –
• Lipid Anandamide AEA Cannabinoid receptors –
• Lipid 2-Arachidonoylglycerol 2-AG Cannabinoid receptors –
• Lipid 2-Arachidonyl glyceryl ether 2-AGE Cannabinoid receptors –
• Lipid N-Arachidonoyl dopamine NADA Cannabinoid receptors TRPV1
• Lipid Virodhamine Cannabinoid receptors –
• Small: Purine Adenosine Ado Adenosine receptors –
• Small: Purine Adenosine triphosphate ATP P2Y receptors P2X receptors
• Small: Purine Nicotinamide adenine dinucleotide β-NAD P2Y receptors P2X receptors

Neuropeptides Category Name Abbreviation Metabotropic Ionotropic

• Bombesin-like peptides Bombesin BBR1-2-3 –
• Bombesin-like peptide Gastrin releasing peptide GRP – –
• Bombesin-like peptide Neuromedin B NMB Neuromedin B receptor –
• Bradykinins Bradykinin B1, B2 –
• Calcitonin/CGRP family Calcitonin Calcitonin receptor –
• Calcitonin/CGRP family Calcitonin gene-related peptide CGRP CALCRL –
• Corticotropin-releasing factors Corticotropin-releasing hormone *CRH CRHR1 –
• Corticotropin-releasing factors Urocortin CRHR1 –
• Galanins Galanin GALR1, GALR2, GALR3 –
• Galanins Galanin-like peptide GALR1, GALR2, GALR3 –
• Gastrins Gastrin Cholecystokinin B receptor –
• Gastrins Cholecystokinin CCK Cholecystokinin receptors –
• Melanocortins Adrenocorticotropic hormone ACTH ACTH receptor –
• Melanocortins Proopiomelanocortin POMC Melanocortin 4 receptor –
• Melanocortins Melanocyte-stimulating hormones MSH Melanocortin receptors –
• Neurohypophyseals Vasopressin AVP Vasopressin receptors –
• Neurohypophyseals Oxytocin OT Oxytocin receptor –
• Neurohypophyseals Neurophysin I – –
• Neurohypophyseals Neurophysin II – –
• Neuromedins Neuromedin U NmU NmUR1, NmUR2 –
• Neuropeptide B/W Neuropeptide B NPB NPBW1, NPBW2 –
• Neuropeptide B/W Neuropeptide S NPS Neuropeptide S receptors –
• Neuropeptide Y Neuropeptide Y NY Neuropeptide Y receptors –
• Neuropeptide Y Pancreatic polypeptide PP – –
• Neuropeptide Y Peptide YY PYY – –
• Opioids Enkephalins δ-Opioid receptor –
• Opioids Dynorphins κ-Opioid receptor –
• Opioids Neoendorphins κ-Opioid receptor –
• Opioids Endorphins μ-Opioid receptors –
• Opioids Endomorphins μ-Opioid receptors –
• Opioids Morphine μ-Opioid receptors –
• Opioids Nociceptin/orphanin FQ N/OFQ Nociceptin receptors –
• Orexins Orexin A OX-A Orexin receptors –
• Orexins Orexin B OX-B Orexin receptors –
• RFamides Kisspeptin KiSS GPR54 –
• RFamides Neuropeptide FF NPFF NPFF1, NPFF2 –
• RFamides Prolactin-releasing peptide PrRP PrRPR –
• RFamides Pyroglutamylated RFamide peptide QRFP GPR103 –
• Secretins Secretin Secretin receptor –
• Secretins Motilin Motilin receptor –
• Secretins Glucagon Glucagon receptor –
• Secretins Glucagon-like peptide-1 GLP-1 Glucagon-like peptide 1 receptor –
• Secretins Glucagon-like peptide-2 GLP-2 Glucagon-like peptide 2 receptor –
• Secretins Vasoactive intestinal peptide VIP Vasoactive intestinal peptide receptors –
• Secretins Growth hormone–releasing hormone GHRH Growth hormone–releasing hormone receptor –
• Secretins Pituitary adenylate cyclase-activating peptide PACAP ADCYAP1R1 –
• Somatostatins Somatostatin Somatostatin receptors –
• Tachykinins Neurokinin A – –
• Tachykinins Neurokinin B – –
• Tachykinins Substance P – –
• Tachykinins Neuropeptide K – –
• Other Agouti-related peptide AgRP Melanocortin receptor –
• Other N-Acetylaspartylglutamate NAAG Metabotropic glutamate receptor 3 (mGluR3) –
• Other Cocaine- and amphetamine-regulated transcript CART Unknown Gi/Go-coupled receptor[16] –
• Other Gonadotropin-releasing hormone GnRH GnRHR –
• Other Thyrotropin-releasing hormone TRH TRHR –
• Other Melanin-concentrating hormone MCH MCHR 1,2 –

Gasotransmitters Category Name Abbreviation Metabotropic Ionotropic

• Gaseous signaling molecule Nitric oxide NO Soluble guanylyl cyclase –
• Gaseous signaling molecule Carbon monoxide CO – Heme bound to potassium channels
• Gaseous signaling molecule Hydrogen sulfide H2S – –