Answer: serotonin

AnswerCrossword Clue
SEROTONINCertain neurotransmitter
SEROTONINNatural mood alterer
SEROTONINNeurotransmitter associated with sleep
serotoninA compound present in blood platelets and serum that constricts the blood vessels and acts as a neurotransmitter
serotonina compound occurring in the brain, acting as a neurotransmitter