Therefore, if you're planning a long journey, you should always apply for the Russian visa before you leave. It's possible to get a tourist visa support at any moment before your journey, however, you can only apply for a tourist visa not earlier than 90 days before the date of your first entry to Russia.
Serotonin is a common neuromediator in the brain. It belongs to the group of so-called biogenic amines, relatively simple chemicals that facilitate the transfer of signals between the cells of the body.
The function of serotonin depends on the region of the brain into which it is released (it also depends on the type of serotonin receptor present in that region). For example, the serotonin neurons in the neocortex in the front of the brain (frontal cortex) regulate cognition, memory, and perceptions.