Abstract:

The biogenic monoamines dopamine (DA), norepinephrine (NE) and serotonin (5-hydroxytryptamine, 5-HT) are major neuromodulators in the mammalian central nervous system (CNS). DA containing neurons are found in i) the mesolimbic system in which cell bodies in the ventral tegmental area (VTA) project axons into the amygdala, cortex, hippocampus and the nucleus accumbens; and ii) the nigrostriatal system in which cell bodies located in the substantia nigra pars compacta send their axons into the dorsolateral parts of the striatum. The central noradrenergic neurons are concentrated in distinct brainstem nuclei with the locus coeruleus (LC) being the most prominent nucleus which projects a diffusely arborizing axonal network to most areas of the CNS. Serotonergic neurons are located in the raphe nuclei in the brain stem with widespread efferent axonal trajectories with a high number of collateral arborizations into many brain regions such as cortical areas, the hippocampus, the basal ganglia and the spinal cord. Malfunctions of the three monoaminergic systems are associated with different psychiatric and neurological diseases such as depression, anxiety, chronic pain, sleep disorders, schizophrenia, various aspects of drug abuse, Parkinson’s disease and Alzheimer’s disease.