Yopobear
Neurotransmetteur
- Inscrit
- 12/11/07
- Messages
- 32
We intake the essential amino acid L-tryptophan through diet. Light photons enter through our pupils and stimulate rods and cones in the back of our eyes, an area called the retina as well as the top of our head, and other thin skinned areas of the body. The energy from light photons is converted to electrical and chemical impulses, which are relayed through a small bundle of nerves, called the optic tract, to the hypothalamus. Information from the hypothalamus is in turn relayed through several other nerve tracts to the pineal gland. (Aronson, 1993) In the pineal gland, tryptophan is converted to serotonin or 5- hydroxy-tryptamine by 5hydroxylation and decarboxylation. Serotonin is used as our predominate daily-waking neurotransmitter. An acetyl group is added to serotonin by an enzyme called serotonin-N-acetyl-transferase (NAT). NAT is believed to be the rate-limiting enzyme, that is, the amount of melatonin produced depends on the activity of this enzyme. Activation of NAT depends not only on signals induced by light hitting the retina, but also from information relayed from other parts of the brain. Adding a methyl group, leading to melatonin follows the acetylation of serotonin. Throughout daylight hours, light reaching the pineal gland prevents the production of melatonin. Even very low intensity light as from an indoor fluorescent light may prevent melatonin release (Laakso, 1993). Light signals reaching the pineal inhibit the activity of the enzyme that converts serotonin to melatonin. Darkness allows melatonin production. Starting in the evening, and throughout the night, the pineal gland releases melatonin, reaching peak levels between 2 and 4 am. In the morning, exposure to light shuts off melatonin production. The chemical name of melatonin is 5-methoxy-N-acetyl-tryptamine. When melatonin is metabolized in the pineal gland, it is converted to 5-methoxy-tryptamine (Hardeland, 1993). 5-methoxy-tryptamine is further metabolized to N, N-dimethyl-5-methoxy-tryptamine (5-MEO-DMT) and other tryptamines. Our brain manufactures its own hallucinogens, which lead us to dream.
from (sOurce)
http://www.lila.info/document_view.phtml?document_id=89
(SEE last AlineA
