This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Opioids, Subject name: Pharmacology
[{'content': 'Mechanism of action of Clonidine in opioid withdrawal syndrome is \nSelect and explain. \nA. b blocking effect, B. Inhibition of opioid receptor, C. Action on a2 presynaptic nerve ending, D. Postsynaptic action', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Action on a2 presynaptic nerve ending Many of the symptoms of opioid withdrawl such as nausea, vomiting, cramps, sweating, tachycardia, and hypertension are a result of loss of opioid suppression of locus ceruleus system during abstinence syndrome. Clonidine is an a2 agonist that reduces adrenergic transmission from locus ceruleus.Clonidine acts on these a2 receptors and supress adrenergic activity in locus ceruleus. (Thus mimicking the action of opioids).In this way it alleviates mainly the autonomic symptoms of opioid withdrawl.Non autonomic symptoms of opioid withdrawl are not affected.", 'role': 'assistant'}]