Isoproterenol FA question

[shouldBstudying]

on page 240 of FA 2011, there's this graph showing how Isoproterenol impacts BP & HR and it shows Isoproterenol causing a transient increase followed by a gradual decrease in systolic BP.

Anyone understand why this is? As a beta1/2 agonsit, shouldn't it slightly increase systolic BP? (i.e. how the graph is drawn in Lippincott's pharm?) Is this an error or is there something else going on I'm not understanding?

Appreciate any guidance

---

Members don't see this ad.

 

[SlaveOfTCMC]

It's likely the reflex response.

At first the B1 increases HR and SV, which should increase SBP and PP.

However, as the HR increases over time, there will be a baroreceptor reflex such that the BP decreases.

Moreover, B2 effects also mediate vasodilation.

 

[sgod34]

on page 240 of FA 2011, there's this graph showing how Isoproterenol impacts BP & HR and it shows Isoproterenol causing a transient increase followed by a gradual decrease in systolic BP.

Anyone understand why this is? As a beta1/2 agonsit, shouldn't it slightly increase systolic BP? (i.e. how the graph is drawn in Lippincott's pharm?) Is this an error or is there something else going on I'm not understanding?

Appreciate any guidance

B1 should increase HR and systolic BP.
B2 should decrease diastolic BP.
So you should he an overal increased HR, with wide PP. The little gradual decrease you see in systolic BP is due to reflex vasodilation secondary to increased contractility by B1.

 

[ArcGurren]

B2 receptors cause vasodilation while B1 causes increased heart rate; vasodilation will lower diastolic pressure (less venous return -> less filling) and as a result you get a widened pulse pressure