Your Brains Anchor to Reality

Serotonin is a very ancient neurotransmitter and has been found in the venom of amphibians, wasps, and scorpions and within the nematocysts of the sea anemone as well as in the nervous system of parasitic flatworms, crickets, and lobsters. Within the human body, 90% of the total serotonin is contained 

THE POWER OF A FEW PERCENT Neurons that produce and release serotonin in the brain are organized into a series of nuclei that lie in a chain along the midline, or seam, of the brainstem these are called the raphe nuclei (raphe means seam in Latin). These neurons project their axons to every part of the brain, and some of these axons make contact with blood vessels the neurons also project downward into the spinal cord. If you were able to insert a recording device into the major raphe nuclei and listen to the activity of your serotonin neurons, you would discover that they have a regular slow spontaneous level of activity that varies little while you are awake. When you fall asleep, the activity of these neurons slows. When you start to dream—or if, as we ll see shortly, you ingest a hallucinogen—these neurons cease their activity completely. 

Despite the relative scarcity of serotonin in your brain, drugs that alter serotonin function can produce profound changes in 

The production of serotonin requires the absorption of the amino acid tryptophan from your food. Transport of this amino acid is influenced by the level of other amino acids in your blood that level, in turn, is also influenced by what you eat. Within the neurons of your brain, tryptophan is converted to 5-hydroxy-tryptophan by tryptophan hydroxylase, an enzyme that is usually not saturated with substrate. Therefore, if you eat less tryptophan, your brain generally produces less serotonin. Conversely, providing additional tryptophan in the diet may lead to increased production of serotonin within neurons. It is worth noting, however, that simply producing more of any neurotransmitter does not guarantee that the neuron will actually release it. If too much serotonin is produced, then the excess is simply discarded. Studies have shown that only extreme depletion or supplementation of this amino acid in the diet can influence serotonin-controlled brain processes such as mood and sleep. 

Moreover, the absence of the release of serotonin in the brain has been correlated with the initiation of hallucinations. This is not to say that we can manipulate our diet to so undermine serotonin release as to experience a hallucination. We cannot. But certain drugs that will initiate this effect, and their action, as well as the experiences they produce, can tell us something about the normal function of serotonin in the brain. 

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