M3 receptor...

[Fungi121]

So a certain qbank of mine is contradicting itself and I'm a bit frustrated. Any help would be mucho appreciated.

Information #1) Taking an M3 agonist = binds to vascular M3 receptors = vasodilation and drop in blood pressure, with reflex tachycardia

Information #2) Atropine does not cause an increase in BP because the M3 receptors have no tone...

How can this happen? Are these both correct?

---

Members don't see this ad.

 

[surgok]

So a certain qbank of mine is contradicting itself and I'm a bit frustrated. Any help would be mucho appreciated.

Information #1) Taking an M3 agonist = binds to vascular M3 receptors = vasodilation and drop in blood pressure, with reflex tachycardia

Information #2) Atropine does not cause an increase in BP because the M3 receptors have no tone...

How can this happen? Are these both correct?

Both are correct. Remember M3 receptors are on blood vessels, but NO parasympathetic nerve supply goes to the blood vessels. This essentially makes those M3 receptors USELESS in-vivo under normal physiologic conditions. When you take exogenous M3 agonist, it will be in the blood stream and it will activate those M3 receptors that are normally not innervated. This will produce vasodilation etc. If you take atropine PRIOR to taking any M3 agonist, atropine alone won't do jack to those M3 receptors because there's no Ach's atropine should antagonize.