Other hormones may be simple amino compounds. Its level goes up at night and decreases with aging. Answer depends on what you've heard. There is a gap, or synapse between one neuron and the next. Neurotransmitters, along with electrical impulses.
Deficiency leads to depressed state.
Diets high in carbohydrates lead to high levels of serotonin and high protein lowers the serotonin concentration. PEA is produced from phenylalanine, an amino acid found in protein-rich foods. Agonists are drugs that mimic the action of other substances, such as hormones and neurotransmitters. Antagonists block the action of hormones and neurotransmitters.