Question

seeking a treatment for schizophrenia, scientists at the munsterlingen asylum in switzerland found that a drug that tweaked the balance of the brains neurotransmitters — the chemicals that control ______, pain and other sensations — sent patients into bouts of euphoria.
ambition
mood
alarm
thrill

Explanation:

Neurotransmitters are known to regulate mood, among other functions like pain and sensations. Euphoria is a mood - related state. Mood is directly controlled by neurotransmitters.

Answer:

B. mood