This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Higher Functions, Subject name: Physiology
The site of action of addictive drugs is: 
Select and explain. 
A. Nucleus raphe magnus, B. Nucleus accumbens, C. Kolliker-Fusenucleus, D. Nucleus parabrachialis
B: Nucleus accumbens
Answer: B: Nucleus accumbens 
Explanation: Nucleus accumbens has a very high population of dopaminergic neurons that act D3 receptors. This area is found to be associated with reward and addictive behavior. Pneumotaxic center is located in the nucleus parabrachialis and Kolliker-Fuse nucleus in upper pons. Nucleus raphe magnus (medulla) has high density of serotonergic neurons and is a component of descending analgesia system.