Serotonin

Social rivalry is part of life for mammals because they live in groups. Reptiles live alone, so they can lunge at attractive food and mating opportunities without worrying about what others will do. If group-living mammals lunged, some would get hurt. Instead, natural selection built a brain that promotes survival by comparing itself to others before acting. When a mammal sees itself as weaker than those around it, cortisol is released (the chemical we know as the "stress hormone") and impulses are restrained. When a brain sees itself as stronger, serotonin is released and it feels safe to act.

The good feeling of serotonin is a great motivator for mammals. Serotonin paves the neural pathways that wire a mammal to expect more in ways that worked before. Cortisol wires a mammal to expect harm from things that triggered it before. Alas, a mammal can't easily avoid stronger members of its herd or pack or troop because isolated individuals are quickly picked off by predators. It just keeps scanning for ways to feel good and avoid feeling bad.

You can feel good about life as a mammal among mammals if you remind yourself that your survival is not actually threatened when your serotonin dips and your cortisol spurts. It just feels that way because you've inherited a brain that promoted survival for 200 million years. In the state of nature, your genes get wiped out if the other guy always gets the banana and the opportunity to mate. It feels like that guy is killing you because from the perspective of your genes, he is. Your brain makes a big deal out of it to make sure that your genes survive. But you can remember that you will be fine without this particular banana, and that your mating opportunity is not actually controlled by the person who just one-upped you.

 https://www.thedodo.com/serotonin-in-monkeys-we-can-le-494428086.html

Small wonder, then, that high serotonin can foster social success. In a classic series of experiments with vervet monkeys, UCLA scientists Michael McGuire and Michael Raleigh found that males who had achieved high rank within a group's social hierarchy had nearly twice as much serotonin in their blood as low-ranking males. But that's not to say they were born leaders; further analysis showed that social standing had as much effect on the animals' serotonin as serotonin had on their status. If an alpha male was displaced by a challenger, his blood count would quickly plummet--and when an upstart came into power, his serotonin level would surge. Raleigh and McGuire found they could deplete a leader's serotonin simply by keeping him behind a one-way mirror, where his peers couldn't acknowledge his dominance displays.

People's social lives are more complicated than monkeys', but not entirely different. When Raleigh and McGuire analyzed blood samples from 48 UCLA fraternity boys, the average serotonin level was nearly 25 percent higher among officers than among members. And when Raleigh compared his own serotonin count with that of his lab director (McGuire), the boss's was 50 percent higher.

Rising to the top may involve some scrapping, but serotonin doesn't foster aggression. ""Serotonin provides a restraint mechanism, a kind of behavioral seat belt,'' says Dr. John Mann of Columbia University. Whether you look at monkeys, dogs, horses or humans, the most aggressive individuals are typically those with the lowest serotonin levels. Drugs that boost serotonin's activity tend to dampen a wide range of impulses (including sexual ones that need no dampening), and they can help violent people get a grip.

Violence is one possible consequence of low serotonin, but there are many others. Without the chemical's leveling effects, we grow more vulnerable to all kinds of impulses--whether to gamble, buy things, steal things or eat things.

You might conclude from all this that more serotonin is always better. But just as a serotonin deficiency can unleash destructive impulses, an overly active serotonin system can leave a person paralyzed by obsessions and compulsions. People with compulsive disorders become hyperaware of potential threats--possibly because serotonin is overstimulating the receptors involved in planning and vigilance--and they develop bizarre rituals for managing their anxiety. 

...tryptophan-rich foods are packed with a variety of amino acids that compete for passage across the blood-brain barrier. Picture a crowd in front of a department store with a single revolving door, says University of Pittsburgh pharmacologist John Fernstrom. ""Tryptophan wants to get in, but it has to stand in line.'' 

Back in the 1970s Fernstrom and Dr. Richard Wurtman of MIT discovered that the best way to shorten that line is simply to eat a carbohydrate. Carbs enter the bloodstream as glucose--and any rise in blood glucose causes the pancreas to secrete insulin. Insulin pushes glucose and various amino acids out of the blood and into fat and muscle cells. But it doesn't mop up tryptophan. So when insulin sweeps through the bloodstream, the crowd at the revolving door disperses and tryptophan glides freely into the brain, where it can be used to make serotonin.



 https://www.newsweek.com/little-help-serotonin-170282