Serotonin is one of the neurotransmitters most commonly associated with depression, and also one of the better-documented neurotransmitters. Most drugs currently used to treat depression focus on this molecule.
Low levels of serotonin are known to cause spur-of-the-moment, aggressive, overly risky activity in people. It also helps with extreme emotions by "toning them down", acting as a calming agent.
Serotonin is derived from an aromatic amino acid known as "5-Hydroxytryptophan," (commonly abbreviated 5-HTP) which in turn is created from an essential amino acid, "L-tryptophan." 5-HTP is very useful in treating depression for a number of reason. It is very easily produced from an African plant "Agriffonia simplicifolia." it is not very reactive with many molecules, and can easily be absorbed into the bloodstream from the intestinal tract. When taken orally, over 70% of the dose will make it into the bloodstream and subsequentally to the brain.
However, Serotonin itself cannot be administered for treatment of depression or a number of disorders that low Serotonin levels are associated with, because the molecule cannot cross the boundary between the bloodstream and the brain.
Administering L-tryptophanĘ would also not be very effective, due to the fact that it is converted into a number of chemicals other than 5-HTP, because a certain enzyme known as tryptophan hydroxylase is needed. This enzyme is not always available, because it is affected by everything from stress to vitamin B6 deficiencies.
Norepinephrine is another one of the major chemicals of depression. However, its main function in the body is dealing with stress (funny how both serotonin and norepinephrine, closely intertwined with depression, are also heavily dependant on stress levels? More on that here). Norepinephrine is released from the adrenal glands under stress, and helps amplify the "flight or fight" syndrome; however, long periods of stress purge the brain of norepinephrine and this is where real problems start to occur.
Norepinephrine has another function, too. It eases learning and remembering, and boosts overall attention/arousal levels. If you have ever experienced stress (and I am sure you have), then you know that when first put under pressure you are running on hyperalert, but after being stressed out for awhile you simply can not think straight, or focus on anything for long periods of time. That is norepinephrine at work.
Norepinephrine is part of the "Tryosine-derived neurotransmitters" family of chemicals. This includes Dopamine and Epinehrine; in fact in the biosynthesis of Norepinephrine (its formation), Dopamine comes one step earlier in the process and Epinephrine a step later. Starting with Tryosine, which the enzyme Tryosine Hydroxylase converts into DOPA, and Tetrahydrobipterin and oxygen molecules are taken in, and Dihydrobiopterin and watermolecules are released. The next step is the conversion of DOPA into Dopamine; this step gives off Carbon Dioxide and uses DOPA decarboxylase as a catalyst to help the conversion. The next step in the process is the conversion of Dopamine into Norepinephrine, which uses Dopamine § Hydroxylase as its helper molecule, and converts oxygen into water molecules in the process. Phenylethanolamine and N-methyltransferase will then convert Norepinephrine into Epinephrine, and as a biproduct will convert S-adenosylmethionine into S-adernosythomocysteine. Whew! I hope you understood half of that.
The "love molecule" is how this particular neurotransmitter is commonly known. In fact, when its chemical make-up was discovered the media went into a frenzy of the possibility of love potions. It hasnt quite come to that point yet (luckily for some of us)... However, it is also released during hard exercise and found in chocolate, and in some people Phenylethylamine can cause headaches by dilating blood vessels in the brain.
Although this particular chemical is not as closely intertwined with depression as Serotonin and Norepinephrine, it is still worth noting as very low levels of Phenylethylamine can make onset of depression more likely. It is because of this neurotransmitter that exercise is often suggested to help combat more mild cases of depression (undoubtedly it helps with worse cases of depression too, but not enough to really contribute to recovery. regardless, getting out and being active never hurt anybody), or just the blues.
Contributing to overall alertness and enhances memory, this is most common neurotransmitter in the body and main communicator between neurons and muscles. It controls the majority of organs. Low levels cause inability to concentrate and forgetfulness.
Schitzophrenia is thought to occur when this neurotransmitter can't reach the frontal lobe of the brain. Normally it gives feelings of happiness and dampens feelings of pain. In the Basil Gangila it helps with execution of smooth and controlled movement. This is also the chemical that turns into Norepinephrine.
Production of this pituitary hormone is stimulated by the presence of Dopamine. It is known to cause muscle contractions and stimulate nerves. Studies have also indicated that the more there is present in the bloodstream, the more attachment there will be in relationships.