Straightjacket, you ask? Yes! Because the number one thing you should remember about alpha-1 receptors is that their activation causes constriction. VASOCONSTRICTION, to be exact. As you may remember from physiology class, blood vessels are wrapped in a layer of smooth muscle. The alpha-1 receptors are all over this smooth muscle, and signal it to contract (thus constricting the blood vessel) when the brain says so.
A drug that is an alpha-1 agonist will cause vasoconstriction. How can this be used therapeutically? Glad you asked! Here are a few therapeutic uses for alpha-1 agonists:
1. Hemostasis. Yes, there are times that we want this to happen! Epinephrine is used topically during surgery to constrict blood vessels and reduce bleeding. Go team!
2. Hand-in-hand with local anesthesia. Vasoconstriction means that drugs can’t flow out of the area so quickly, so adding an alpha-1 agonist makes the anesthetic effect last longer!
3. Sniffle-bashing, AKA nasal decongestion! The main ingredients of many cold medicines, pseudephedrine and phenylephrine, are both alpha-1 agonists. When they shrink the blood vessels in your nose, you become less congested.
4. Okay, I lied a little bit. There is a use for alpha-1 agonists that has nothing to do with vasoconstriction. They do one more thing, and that is they cause the pupils to dilate. This is called mydriasis. Alpha-1 agonists are often added to the solution squirted on your eyeball at the opthamologist’s office.