Glutamic acid
Glutamate is also a neurotransmitter (see below), which makes it one of the most abundant molecules in the brain. Malignant brain tumors known as glioma or glioblastoma exploit this phenomenon by using glutamate as an energy source, especially when these tumors become more dependent on glutamate due to mutations in the gene "IDH1".
Serotonin
The neurons of the raphe nuclei are the principal source of 5-HT release in the brain.
There are nine raphe nuclei, designated B1-B9, which contain the majority of serotonin-containing neurons (some scientists chose to group the "nuclei raphes lineares" into one nucleus), all of which are located along the midline of the brainstem, and centered on the reticular formation.
Axons from the neurons of the raphe nuclei form a neurotransmitter system reaching almost every part of the central nervous system. Axons of neurons in the lower raphe nuclei terminate in the cerebellum and spinal cord, while the axons of the higher nuclei spread out in the entire brain.