You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Clonidine is used as an antihypeensive agent but if used as a fast intravenous injection, it can increase the blood pressure due to: and explain in detail?
Alpha 2 receptors are present both presynaptically as well as postsynaptically. Clonidine acts as presynaptic a2 agonist and decreases the central sympathetic outflow. However, it can also act on vascular postsynaptic a2 receptors, leading to vasoconstriction and increase in blood pressure. Chances of this reaction is more when clonidine is administered by quick i.v. injection.