Muscarinic acetylcholine receptor M3

The second force is going to tighten it.

So you have a vagus nerve is going to release acetylcholine onto M3 muscarinic receptors.

That's going to activate phospholipase C, which makes IP3.

And then IP3 is going to release calcium from its stores inside the cell.

So beta-2 agonists are going to make more cyclic AMP.

You have drugs like your methylxanthines that's going to stop the breakdown of cyclic AMP.

You have anticholinergics that's going to block the M3 receptor.

And you have volatile anesthetics and magnesium that's going to lower calcium.

So vasopressin raises vascular tone through GQ too, but through its own V1a receptors on vascular smooth muscle.

Muscarinic M3 receptors are another GQ example.

In the airway, M3 activation promotes smooth muscle contraction and gland secretion.

That's why an antimuscarinic like ipratropium helps with cholinergic bronchoconstriction.

Antimuscarinic means it blocks muscarinic acetylcholine receptors.