feedback mechanism in decongestan tachyphilaxis?

[bolt usmle]

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Hi,friends.. I am doing uworld and i found a real strange answer from uworld...it is about the decongestan...they said that decongestan tachyphilaxis is because of negative feedback..? I have never heard that cathecolamins have any negative feedback mechanism.. Anybody knows about this?thank you 🙂

 

[Apoplexy__]

Eh, I'm sure it's not important. I got the Q too, and I just assumed it was the pre-synaptic a2 receptors. Those receptors are known to be a quick-acting physiological mechanism of negative feedback for some adrenergic systems. Remember a2 is Gi, so it causes decreased cAMP in the presynaptic terminal upon stimulation.