sustained decrease in heart rate no relation norepinephrine
Mechanism of action
It stimulates α1 and α2 adrenergic receptors to cause blood vessel contraction, thus increases peripheral vascular resistance and resulted in increased blood pressure. This effect also reduces the blood supply to gastrointestinal tract and kidneys. Norepinephrine acts on beta-1 adrenergic receptors, causing increase in heart rate and cardiac output.  However, the elevation in heart rate is only transient, as baroreceptor response to the rise in blood pressure as well as enhanced vagal tone ultimately result in a sustained decrease in heart rate. Norepinephrine acts more on alpha receptors than the beta receptors.
no relation