Musiciаns аnd stаge perfоmers typically experience crippling stage fright, that despite perfоrming fоr a living, in the lead up to taking the stage they experience body sweats, distress, and difficulty relaxing. To offset this, doctors will prescribe propranolol, a beta adrenergic drug, that is an antagonist for a specific type of noradrenergic receptors. As a result, this drug is effective due to it primarily countering the actions of the _____________.