This 2014 human study showed how oxytocin regulates serotonin with the involvement of the right part of the amygdala.

The following passage caught my eye as a possible explanation of why more women than men prefer horror movies: oxytocin?

“We have chosen to enroll male subjects only to avoid the confounding effects linked to sex and a possible interaction with gonadal steroids. Indeed, as shown by previous studies, oxytocin modulates brain activity differently in male and female subjects.

For instance, oxytocin suppresses amygdala response to emotionally threatening stimuli in males but enhances the same response in females.“

http://www.pnas.org/content/111/23/8637.full “Switching brain serotonin with oxytocin”