Neurotransmitters
The human brain consists of approximately 86 billion neurons that communicate through neurotransmission, where chemical messages called neurotransmitters are passed across the synapse, the gap between cells. These endogenous molecules are released from synaptic vesicles when a neuron is activated and interact with specific receptors on neighboring cells, influencing the strength of the signal transmitted in neural circuits.
| Neurotransmitter | Type | Neurons | Receptors | Brain Parts/Nuclei |
|---|---|---|---|---|
| Acetylcholine (ACh) | Small-molecule | Cholinergic neurons | Nicotinic, Muscarinic | Basal forebrain, brainstem nuclei |
| Dopamine (DA) | Small-molecule | Dopaminergic neurons | D1, D2, D3, D4, D5 | Substantia nigra, ventral tegmental area (VTA), hypothalamus |
| Glutamate (GLU) | Small-molecule | Glutamatergic neurons | NMDA, AMPA, Kainate, Metabotropic Glutamate Receptors (mGluRs) | Cortex, hippocampus, amygdala |
| Serotonin (5HT) | Small-molecule | Serotonergic neurons | 5-HT1, 5-HT2, 5-HT3, 5-HT4, 5-HT6, 5-HT7 | Raphe nuclei |
| Norepinephrine (NE) | Small-molecule/Hormone | Noradrenergic neurons | Alpha (α1, α2), Beta (β1, β2, β3) | Locus coeruleus, lateral tegmental area |
| gamma-Aminobutyric acid (GABA) | Small-molecule | GABAergic neurons | GABA-A, GABA-B | Widespread in the brain (e.g., cortex, hippocampus, striatum) |
| Oxytocin | Neuropeptide/Hormone | Neurons in the hypothalamus | Oxytocin receptor (OXTR) | Paraventricular nucleus, supraoptic nucleus |
| Vasopressin | Neuropeptide/Hormone | Neurons in the hypothalamus | V1a, V1b, V2 | Paraventricular nucleus, supraoptic nucleus |
| Corticotropin-releasing factor (CRF) | Neuropeptide | CRF-releasing neurons in the hypothalamus | CRF1, CRF2 | Paraventricular nucleus of the hypothalamus |
| Galanin | Neuropeptide/Co-transmitter | Galaninergic neurons | GALR1, GALR2, GALR3 | Various nuclei, including the hypothalamus and brainstem |
| Enkephalin | Neuropeptide/Co-transmitter | Enkephalinergic neurons | Delta-opioid receptor (DOR), Mu-opioid receptor (MOR) | Striatum, amygdala, spinal cord |
| Dynorphin | Neuropeptide/Co-transmitter | Dynorphin-releasing neurons | Kappa-opioid receptor (KOR) | Striatum, hypothalamus |
| Neuropeptide Y | Neuropeptide/Co-transmitter | Neuropeptide Y-releasing neurons | Y1, Y2, Y4, Y5 | Hypothalamus, cortex |