Answer: Dopamine Obsessive-compulsive disorder (OCD) is linked to defects in the cortico-striatal-thalamic-cortical (CSTC) circuitry, which may be linked to neurotransmitter dysregulation throughout this network. Serotonin, dopamine, glutamate, and -aminobutyric acid (GABA) are the main neurotransmitters throughout the CSTC. Compulsive behaviors linked to OCD are likely the product of a related dopaminergic reward system dysfunction. Continuous ventral striatum activation may lead to an undirected expectation of reward. Anxiety and a desire to fill the gap are caused by unfulfilled expectations. Step-by-Step explanation References Richter, M. A., De Jesus, D. R., Hoppenbrouwers, S., Daigle, M., Deluce, J., Ravindran, L. N., ... & Daskalakis, Z. J. (2019). Evidence for cortical inhibitory and excitatory dysfunction in obsessive compulsive disorder. Neuropsychopharmacology, 37(5), 1144-1151. Pittenger, C., Krystal, J. H., & Coric, V. (2016). Glutamate-modulating drugs as novel pharmacotherapeutic agents in the treatment of obsessive-compulsive disorder. NeuroRx, 3(1), 69-81. 1 points QUESTION 2 1. Select the class of drugs most effective in treating pain disorder. Answer: A Opioid analgesics . B TCA and SSRI . antidepressants C Beta-adrenergic . blockers D Mood stabilizers . Opioids analgesics