This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
Ascending pain pathway is inhibited in dorsal midbrain by 
Select and explain. 
A. 5-HT (serotonin), B. Noradrenaline 1, C. Substance P, D. Glutamate
A: 5-HT (serotonin)
Answer: A: 5-HT (serotonin) 
Explanation: The cell bodies of serotonin containing neurons are localized in the raphe nuclei of midbrain and brainstem. ... Serotonin therefore acts descending pathway to modulate spinal pain signals Ref: guyton and hall textbook of medical physiology 12 edition page number:699,700,701