| Neurotransmitter | Site of Synthesis | ↑ in Disease | ↓ in Disease | Comments |
| Acetylcholine (ACh) | Basal nucleus of Meynert | Parkinson’s disease | Alzheimer’s diseaseHuntington’s disease | Involved in learning and memory in the central nervous system (CNS)All motor neurons to skeletal muscles use AChAll preganglionic neurons use ACh at the ganglion of the parasympathetic and sympathetic systemPostganglionic parasympathetic fibers use AChPresynaptic neurons of the adrenal medulla use ACh |
| Dopamine | Ventral tegmentumSubstantia Nigra pars compactaArcuate nucleus (tubuloinfundibular pathway) | Huntington’s diseaseSchizophrenia | Parkinson’s diseaseDepression | Also known as prolactin-inhibiting factorantipsychotics (dopamine antagonists) can lead to increased prolactin secretion → galactorrhea and amenorrheaInvolved in movement and working memoryInvolved in addiction |
| γ-Aminobutyric acid (GABA) | Nucleus accumbens | – | Huntington’s diseaseAnxiety | Major inhibitory neurotransmitter of the brainglycine is the major inhibitory neurotransmitter in the spinal cordBenzodiazepines act on GABA receptors to enhance GABA activityBaclofen is a GABA B receptor agonist that relieves spasticity |
| Norepinephrine (NE) | Locus ceruleus | Anxiety | Depression | Involved in mood control and sleep-wake cyclePostganglionic sympathetic fibers release NEimportant for maintaining blood pressure |
| Serotonin (5-HT) | Raphe nucleus
| – | DepressionAnxiety | Serotonin re-uptake inhibitors (SSRIs) are effective in treating depression, anxiety disorders, obsessive compulsive disorderSerotonin syndromesecondary to high levels of sertonin (e.g., MAO inhibitor + SSRI) |
