Figure 1. Monoaminergic neurons innervate almost all brain areas. A. Noradrenaline. The noradrenergic neurons of the locus ceruleus project to the limbic and cortical regions, and to the thalamus, cerebellum, and spinal cord. They play an important role in the regulation of mood and attention. The noradrenergic neurons of cell groups A1 , A2, A5, and A7 project to more restricted regions.4 They are important for autonomic function. B. Dopamine. The dopaminergic neurons of the substantia nigra and the adjacent ventral tegmenta! area (VTA) project to the striatum and to regions in the neocortex. They are important in the initiation of movements and for emotional processes. Furthermore, there is a dopaminergic cell group in the hypothalamus that regulates neuroendocrine processes. C. Serotonin. The serotonergic neurons located in the raphe nuclei project to almost all parts of the brain and are involved in many functions including the regulation of emotional processes. D. Histamine. Histaminergic neurons are located in the tuberomammillary complex of the hypothalamus. They project to all parts of the brain and are important for arousal (the excited brain state). Modulation of neuronal activity by these monoamines is an important factor of well-balanced central nervous activity. Stress leads to hyperactivity of the monoamine neurons and thus to a dysregulation of neuronal activity. Currently available antidepressants are thought to adjust the balance between the different neurotransmitter systems.
