Saturday, November 26, 2011

Vasomotor reversal of Dale

Do you know that a particular neurotransmitter can act on different types of receptors?
So it's not the neurotransmitter but the receptor on which the response depends upon
Hence depending upon the receptor a varied effect is obtained! :O

An awesome example of this is the neurotransmitter adrenaline.
It acts on two types of receptors.. Alpha and beta receptors.
Alpha receptors cause vasoconstriction where as beta receptors mediate vasodilation.
Beta receptors are more sensitive.

So large i.v. infusion of adrenaline causes vasoconstriction which increases blood pressure via the alpha receptors.
But after a while, there is a re-uptake and dissipation of adrenaline.
This decreases the adrenaline concentration.
Which doesn't stimulate the alpha receptors but is enough to stimulate the sensitive beta receptors.
Hence there a secondary fall in blood pressure.

Vasomotor reversal of Dale
So what happens if you block only the alpha receptors?
A fall in blood pressure due to beta mediated vasodilation!
This is known as vasomotor reversal of Dale :D

To be specific, the receptors involved are Alpha 1 and Beta 2 receptors.
You may remember the mnemonic, ABCD, Alpha - Constriction, Beta - Dilation! :D

That's all!

Have an amazing weekend! :)


Updated: Mnemonic on 28 Nov, 2013.
Related posts: Noradrenaline and adrenaline mnemonic


  1. you seem to be having a great time in the class room :P

    1. Haha yes, I randomly doodle in my notebook during class and this is a picture of it =D

  2. Thank you for this awesome and funny explanation~ it is really helpful in understanding.. Thanks again <3

  3. wow! I wish I was as enthusiastic as you are, when it comes to studying. Thanks!

    1. Oh well, I'm glad you could use my enthusiasm! Hope you rock studies in your own unique way :)

  4. Thanks for the explanation.........and it was a great explanation......

  5. Nicely explained...!!

  6. Brother This is a biphasic response of adrenaline not Reversal of dale

  7. awesome and fun explanation! keep up the good work :)
    P.S u can add a little bit of extra info here, i.e the receptors are specifically the Alpha1 and Beta2 receptors and for easy remembering their function there is a minemonic ABCD, alpha constriction and beta dialation :D

    1. Thank you so much for the compliments and the mnemonic ^_^
      I'll update this post with the receptors and extra info soon :)

  8. can you explain re-reversal of vasomotor reversal seen after adminsteration of propanolol ? ( its written in my textbook )
    and if u say,, we block alpha receptors - so there is vasodilation due to beta receptors ;
    what happens when we block beta receptors?
    B blockers are also used to treat hypertension.. how? :/

    1. We said that after administration of a alpha blocker, we saw a fall in blood pressure.
      Then, let's say, we administer propanolol.
      Propranolol blocks beta receptors, so it will gradually cause rise in BP.
      This is rereversal of Dale’s vasomotor reversal.

    2. Why are beta blockers used to treat hypertension?
      Umm.. There is a long explanation for that.. You're probably in the beginning of your term (and textbook) right now.. It used to bother me as well (You're not the only one!)

      I'll explain in short but you'll get this gradually once you understand the cardiovascular system, you'll have to be patient in understanding things for now.

      Beta blockers will cause a rise in total peripheral resistance but that is not why it is used in hypertension.. There are other "mechanisms" that when seen in the bigger picture are beneficial to patients who have hypertension.
      They block the renin angiotensin aldsterone system (The system that retains salt and water and causes hypertension!)
      Beta blockers also reduce cardiac work (Life saving for the ischemic heart who has to do more work with less blood!)

      Like I said, you'll get this eventually.. Lemme know if you have any other doubts =)

    3. Thank you :) , got the rereversal .. n i'm starting to read drugs used to treat hypertension for that explaination.. n i understood about beta blockers blocking RAAS ( renin angiotension aldosterone system ). Again, thanks for explaining it to me :)

  9. could you please suggest me which books i should refer for pharmacology which makes it simpler? The drug names confuse me soo much, glipizide, pioglitazone, nateglinide, pramlintide .. oh my .. i wake up everyday n revise them first thing, still my brain manages to mix it all up.. :/ or a suggestion( like writing the drug name 50 times or something) or a site which will help me with learning?

    And also, could you please share about cestodes, trematodes and nematodes ? like .. how did you learn the names of the parasites and the lifecycles.. they are too complicated. :(

    Thank you.

    1. For getting the concepts right, Katzung is supremo. It'll take time to get a hang of the names.. If mnemonics work for you, you should try making em! Try to put mechanism in the mnemonic to make it simpler (That's what I do!)

      I drew, revised and revised for remembering life cycles. Memorized and forgot xD

    2. Here are some recent examples of how I make my pharmacology mnemonics -

      This one is the only parasitology post I've written:

    3. Thank you for making things easier :)

  10. Hey does d action of adrenaline on beta 1 receptors in d heart come under dale's vasomotor reversal? ?

  11. Great stuff man. .kudos!

  12. really nice explanation!! :)

  13. Great, thank u so much.

  14. Your explanation makes things much more easier..:-) Thanks a lot:-)


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