This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
[{'content': 'Vasomotor reversal phenomenon after administration of an a adrenergic blocker is seen with \nSelect and explain. \nA. Noradrenaline, B. Isoprenaline, C. Adrenaline, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Rapid i.v. injection of Adr produces a marked increase in both systolic as well as diastolic BP (at high concentration a response predominates and vasoconstriction occurs even in skeletal muscles). The BP returns to normal within a few minutes and a secondary fall in mean BP follows. The mechanism is--rapid uptake and dissipation of Adr - concentration around the receptor is reduced - low concentrations are not able to act on a receptors but continue to act on b2 receptors. When an a blocker has been given, only fall in BP is seen--vasomotor reversal of Dale. Ref:- kd tripathi; pg num:-131', 'role': 'assistant'}]