Chemicals in the Brain
Most chemicals found in the brain are neurotransmitters, chemicals used to relay, amplify, and modulate the electrical signals passed between neurons and other cells.
The neurotransmitters found in the brain consist primarily of small-molecule transmitters (a class of about ten molecules), and more than fifty neuroactive peptides or proteins. Some fatty acids may also be neurotransmitters, as are several single ions like synaptically-released zinc.
Though the chemicals in the brain vary, their effect is determined by the receptor they go to, not by the chemicals themselves.
The small-molecule neurotransmitter molecules are generally packaged in vesicles, and their release is triggered by synaptic depolarization which causes calcium ion channels to open and release the neurotransmitter; the whole process is called exocytosis. Neurotransmitters released in this way diffuse across the synaptic divide to bind to receptors. Peptides are synthesized in the neuron's soma and transmitted through the axon to the synaptic divide; otherwise, the mechanism of release is similar.
Neurotransmitters are often removed from the synaptic divide by a process called reuptake or uptake; this clears the channel so that the neuron is no longer stimulated or inhibited. With acetylcholine and some other neurotransmitters, the mechanism is digestion by an enzyme instead, or dissolution by proteases. Most neuroactive drugs take advantage of these removal mechanisms to affect the brain.
A list of common neurotransmitters:
Derived from amino acids
aspartate
glutamate (Glu)
γ-aminobutyric acid (GABA)
glycine (Gly)
Biogenic amines
acetylcholine (Ach)
Monoamines (in order of synthesis)
-from phenylalanine and tyrosine:
dopamine (DA)
norepinephrine or noradrenaline (NE)
epinephrine or adrenaline (Epi)
-from tryptophan:
serotonin (5-hydroxytryptamine, 5HT)
melatonin (Mel)
-from histidine:
histamine (H)
Polypeptides (or neuropeptides)
bombesin
gastrin releasing peptide (GRP)
Gastrins
gastrin
cholecystokinin (CCK)
Neurohypophyseals
vasopressin
oxytocin
neurophysin I
neurophysin II
Neuropeptide Y
neuropeptide Y (NY)
pancreatic polypeptide (PP)
peptide YY (PYY)
Opioids
corticotropin (adrenocorticotropic hormone, ACTH)
Beta-lipotropin
dynorphin
endorphin
enkephaline
leumorphin
Secretins
secretin
motilin
glucagon
vasoactive intestinal peptide (VIP)
growth hormone-releasing factor (GRF)
Somatostatins
somatostatin
Tachykinins
neurokinin A
neurokinin B
neuropeptide A
neuropeptide gamma
substance P
Other neurotransmitters
nitric oxide (NO) no receptor
carbon monoxide (CO)
anandamide
Besides neurotransmitting chemicals, many other chemicals found in the brain function as precursors or building blocks to neurotransmitters. Additionally, the cerebrospinal fluid of the brain which provides protection, nutrition and buoyancy to the brain is a clear fluid that contains traces of glucose and various proteins. And of course, the brain's neuron and glial cells have unique cellular and chemical structures as well.
Web Resources On Chemicals in the Brain
Brain Chemicals
About Neurotransmitters
Book Resources On Chemicals in the BrainThe Chemical Brain: The Neurochemistry of Addictive Disorders by Sidney Cohen
Understanding the Brain and Its Development: A Chemical Approach by Harun K. M. Yusuf
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