Serotonin increases activity in neural circuits, leading to feelings of satiety and quieting motivated behaviors.

“Serotonin is a neuromodulator that tends to increase the activity of certain neural circuits, including within the hypothalamus, but also within the body that trigger a sense of satiety, of having enough, enough food, enough warmth, enough social connection, enough of any motivated goal or drive or any type of thing or behavior that one would want more of, serotonin tends to make those circuits quiet down.”