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018 Agonists and Antagonists

In this video, watch as Leslie explains how agonists and antagonists affect the receptor sites of the cell.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel. In this episode, Episode 18, I’m going to be talking about agonists and antagonists. It almost sounds like a plot for a movie, but it’s not a movie, unless it’s a movie happening inside your body. Anyhow, for today, let’s get into what we’re going to be talking about.

The first thing we’re going to talk about is “What is an agonist?” An agonist is a molecule that mimics the effect of a neurotransmitter, so it does what that neurotransmitter would normally do. An example of that would be succinylcholine mimics the neurotransmitter acetylcholine. So what I’m going to do is I’m going to draw the receptor here, and here we have the cell membrane of the neuron. I’m going to draw it a little different than I’ve been drawing it before. I’m going to have these as the receptor sites. This is where the acetylcholine normally binds to the nicotinic receptor.

I’m going to draw acetylcholine here, but I’m not going to draw it coming here. What I’m going to do is I’m going to draw something that’s slightly different, let’s just say it’s a different color. It’s a similar shape to acetylcholine, and we’re going to call this succinylcholine. When that comes here and it binds to the receptor, same thing here, it comes and it binds to the receptor, the channel opens, which is what it would normally do if acetylcholine binds. And then, sodium ions on the outside end up coming inside the cell. So this would be an example of an agonist. It’s not acetylcholine, it’s something else, and let’s say, in this case, it’s succinylcholine, and that comes, binds to the receptor and causes a similar response. That is an agonist.

Now, let’s look at what an antagonist is. You can probably guess just by reading the word, but an antagonist is a molecule that opposes the effect of a neurotransmitter. So it does the exact opposite. An example of that would be curare, which is an antagonist to acetylcholine that can actually block the binding sites for acetylcholine. So here, we have our nicotinic receptor again, and it’s in the membrane of the cell, and here we have the binding sites.

Out here, we have acetylcholine that wants to bind. However, we have something else that’s around that’s not exactly like acetylcholine and let’s say that its shape looks something like this. That binds to the receptor, and what that does is it blocks the receptor site. So acetylcholine wants to bind and it wants to cause that channel to open, but it’s being blocked so that it cannot bind, and it cannot open the channel for sodium to come in. This would be an example of what curare does. It’s an antagonist, and in fact, curare can cause muscles to become paralyzed because they cannot be activated and sodium cannot rush into the cell, exciting the cell, and exciting the muscle to contract. So that can be a serious thing if you have curare binding to these receptor sites.

That’s really all for this video. I hope you understand the difference between an agonist and an antagonist. If you have any questions or comments about that, go ahead and leave them below. I’ll be happy to answer your question, and maybe even make a follow-up video answering your specific question. That’s it for this video, and I’ll see you on the next one.

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Leslie Samuel is the creator of Interactive Biology. His mission is to use this site to Make Biology fun for people all over the world.

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Leave An AWESOME Comment

119 Responses to “018 Agonists and Antagonists”

  1. tara February 5, 2011 at 6:53 am #

    are the shapes of the agonists and receptor sites similair?

    • Leslie February 5, 2011 at 6:05 pm #

      Hi Tara,

      That’s an excellent question. You got it right. It all has to do with having the right shape to fit into the binding site so that it’s able to trigger a response.

  2. InteractiveBiology February 10, 2011 at 4:53 pm #

    @MrSandman0311 You’re welcome :)

  3. DatNigerian March 6, 2011 at 2:10 pm #

    Dude you don’t know how grateful i am that you are out there breaking down
    this terms and concepts. am currently taking a physiology class and its a
    killer to comprehend but your illustration makes it easier to grasp and
    understand. THANK YOU

  4. InteractiveBiology March 6, 2011 at 2:19 pm #

    @DatNigerian That’s awesome man. Glad to know it’s helping!

  5. TimmysMummy March 21, 2011 at 5:22 am #

    Hey :) not only do your videos help me understand but also REMEMBER this stuff, which is the important part for the exams isnt it!! PLEASE dont stop making these videos.

  6. TimmysMummy March 21, 2011 at 5:22 am #

    Hey :) not only do your videos help me understand but also REMEMBER this stuff, which is the important part for the exams isnt it!! PLEASE dont stop making these videos.

  7. InteractiveBiology March 21, 2011 at 8:35 am #

    @TimmysMummy That’s awesome to hear. Thanks for the feedback. And don’t worry, I’ll be making these videos for a while :)

  8. varsha April 17, 2011 at 9:20 am #

    does he the binding of the antagonists occur at random or in response to some disorder??

  9. Jourdyn April 17, 2011 at 11:22 pm #

    You videos are awesome for helping with my cell biology class! My teacher just does not explain this stuff as well as you do! Thanks!

    • Leslie April 17, 2011 at 11:27 pm #

      That’s Awesome Jourdyn,

      Glad to know you are finding value in the videos. I plan on expanding a lot on what’s here, so make sure to stay tuned :)

      All the best!

  10. 2joann May 29, 2011 at 2:58 pm #

    Suppose your given a graph that indicates the frequency of action potentials firing. There are 4 drugs and two bar graphs for each drug indicating the frequency of stimulation and no stimulation. If a drug shows that there’s an increase of stimulation of Drug A, but also an increase in no stimulation. Should we assume this molecule A is an antagonist? Based on your video, this is what I have analyzed.

  11. 2joann May 29, 2011 at 2:58 pm #

    Suppose your given a graph that indicates the frequency of action
    potentials firing. There are 4 drugs and two bar graphs for each drug
    indicating the frequency of stimulation and no stimulation. If a drug shows
    that there’s an increase of stimulation of Drug A, but also an increase in
    no stimulation. Should we assume this molecule A is an antagonist? Based on
    your video, this is what I have analyzed.

  12. InteractiveBiology May 29, 2011 at 4:02 pm #

    @2joann I’m a little confused by what you mean with an increase in stimulation and an increase in no stimulation. Can you clarify?

  13. InteractiveBiology May 29, 2011 at 4:02 pm #

    @2joann I’m a little confused by what you mean with an increase in
    stimulation and an increase in no stimulation. Can you clarify?

  14. FarhadTv July 8, 2011 at 6:34 am #

    Is paroxetin an agonist or antagonist?

    And what does ketamine do?

  15. Farhad Afghan July 8, 2011 at 6:34 am #

    Is paroxetin an agonist or antagonist? And what does ketamine do?

  16. InteractiveBiology July 8, 2011 at 9:14 am #

    Paroxetine is an antagonist to the neurotransmitter serotonin.
    Ketamine is an antagonist that acts on the NMDA receptor, which is a receptor for glutamate.

  17. InteractiveBiology July 8, 2011 at 9:14 am #

    Paroxetine is an antagonist to the neurotransmitter serotonin. Ketamine is
    an antagonist that acts on the NMDA receptor, which is a receptor for
    glutamate.

  18. diphot1 July 10, 2011 at 3:07 am #

    ur simply superb in explaining things clearly, i luv the way ur conveying things to us…. thanks a lot dude

  19. dip hot July 10, 2011 at 3:07 am #

    ur simply superb in explaining things clearly, i luv the way ur conveying
    things to us…. thanks a lot dude

  20. InteractiveBiology July 10, 2011 at 9:05 am #

    @diphot1 You’re very much welcome. Glad to know you are finding value in the videos!

  21. hally003 July 12, 2011 at 2:01 am #

    Brilliant!! Thank you SO much :)

    Can anyone help me understand the effects of an agonist at glutamate receptors?

  22. hally003 July 12, 2011 at 6:01 am #

    Brilliant!! Thank you SO much :)

    Can anyone help me understand the effects of an agonist at glutamate receptors?

  23. MultiverseQueen August 4, 2011 at 8:32 am #

    Thank you SO SO much!! I seriously cannot tell you how helpful this is to me right now. I’m at my wits end trying to mentally go through the process. I’ll search through the vids to see if you cover everything I’m trying to learn like the specifications on things like the SSRIs etc.

  24. InteractiveBiology August 4, 2011 at 8:48 am #

    @MultiverseQueen You are very much welcome. Glad to know it’s helping. I have many others. I haven’t covered SSRIs as yet, but that will probably come at some point. All the best!

  25. InteractiveBiology August 4, 2011 at 8:48 am #

    You are very much welcome. Glad to know it’s helping. I have many others. I haven’t covered SSRIs as yet, but that will probably come at some point. All the best!

  26. MultiverseQueen August 4, 2011 at 12:32 pm #

    Thank you SO SO much!! I seriously cannot tell you how helpful this is to me right now. I’m at my wits end trying to mentally go through the process. I’ll search through the vids to see if you cover everything I’m trying to learn like the specifications on things like the SSRIs etc.

  27. InteractiveBiology August 4, 2011 at 12:48 pm #

    You are very much welcome. Glad to know it’s helping. I have many others. I haven’t covered SSRIs as yet, but that will probably come at some point. All the best!

  28. ta88iv September 29, 2011 at 2:31 am #

    How can an agonist become an antagonist?

  29. ta88iv September 29, 2011 at 2:31 am #

    How can an agonist become an antagonist?

  30. ta88iv September 29, 2011 at 6:31 am #

    How can an agonist become an antagonist?

  31. InteractiveBiology October 2, 2011 at 12:57 am #

    @ta88iv All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions.

    All the best

  32. InteractiveBiology October 2, 2011 at 4:57 am #

    All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions.

    All the best

  33. ninhbac04 October 12, 2011 at 5:45 pm #

    perfect

  34. InteractiveBiology October 12, 2011 at 5:45 pm #

    @ninhbac04 Thanks :)

  35. ninhbac04 October 12, 2011 at 9:45 pm #

    perfect

  36. InteractiveBiology October 12, 2011 at 9:45 pm #

    Thanks :)

  37. MayokoLove October 19, 2011 at 9:05 pm #

    …..does the nervous system ever end? :-/ lol

  38. swissdedicated November 4, 2011 at 2:25 pm #

    easy, simple, perfect. great work sir, your effort is greatly appreciated

  39. swissdedicated November 4, 2011 at 6:25 pm #

    easy, simple, perfect. great work sir, your effort is greatly appreciated

  40. 1alghanmi November 16, 2011 at 11:19 pm #

    thank you very much

  41. 1alghanmi November 16, 2011 at 11:19 pm #

    thank you very much

  42. abdullah alghanmi November 17, 2011 at 4:19 am #

    thank you very much

  43. abdullah alghanmi November 17, 2011 at 4:19 am #

    thank you very much

  44. abdullah alghanmi November 17, 2011 at 4:19 am #

    thank you very much

  45. InteractiveBiology November 17, 2011 at 6:18 am #

    @1alghanmi You’re very welcome. Stay tuned for more Biology videos coming very soon!

  46. InteractiveBiology November 17, 2011 at 6:18 am #

    You’re very welcome. Stay tuned for more Biology videos coming very soon!

  47. InteractiveBiology November 17, 2011 at 6:18 am #

    @swissdedicated Thank you! Please stay tuned for more Biology videos to be uploaded to the website soon!

  48. InteractiveBiology November 17, 2011 at 6:18 am #

    Thank you! Please stay tuned for more Biology videos to be uploaded to the website soon!

  49. InteractiveBiology November 17, 2011 at 11:18 am #

    You’re very welcome. Stay tuned for more Biology videos coming very soon!

  50. InteractiveBiology November 17, 2011 at 11:18 am #

    Thank you! Please stay tuned for more Biology videos to be uploaded to the website soon!

  51. msss432 November 19, 2011 at 1:23 am #

    where do agonists and antagonists come from? How are they produced and hw do they get to the synaptic cleft?

  52. msss432 November 19, 2011 at 6:23 am #

    where do agonists and antagonists come from? How are they produced and hw do they get to the synaptic cleft?

  53. InteractiveBiology November 20, 2011 at 3:16 am #

    @msss432 Unfortunately, Leslie won’t be able to answer any specific questions as he is busy creating videos and content for the site. He will get to more Biology topics so, please stay tuned for more!

  54. InteractiveBiology November 20, 2011 at 3:16 am #

    Unfortunately, Leslie won’t be able to answer any specific questions as he is busy creating videos and content for the site. He will get to more Biology topics so, please stay tuned for more!

  55. InteractiveBiology November 20, 2011 at 8:16 am #

    Unfortunately, Leslie won’t be able to answer any specific questions as he is busy creating videos and content for the site. He will get to more Biology topics so, please stay tuned for more!

  56. msss432 November 21, 2011 at 5:05 pm #

    @InteractiveBiology so can someone answer my question?

  57. msss432 November 21, 2011 at 5:05 pm #

    so can someone answer my question?

  58. msss432 November 21, 2011 at 10:05 pm #

    so can someone answer my question?

  59. InteractiveBiology November 22, 2011 at 6:23 am #

    @msss432 Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  60. InteractiveBiology November 22, 2011 at 6:23 am #

    Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  61. InteractiveBiology November 22, 2011 at 11:23 am #

    Hi! I’m so sorry, but Leslie is busy with a lot of stuff right now. He just doesn’t have the time to be able to go through each mail he gets but, he’s working on more videos and he might just touch more about this topic. So, please stay tuned for more! You can try to go to our Facebook Fan Page community, too. There are some who would answer Biology inquiries from there.

  62. xamandaxgatewayx December 24, 2011 at 12:05 pm #

    @msss432 drugs can be examples of antagonists or agonists.

  63. xamandaxgatewayx December 24, 2011 at 12:05 pm #

    drugs can be examples of antagonists or agonists.

  64. xamandaxgatewayx December 24, 2011 at 12:08 pm #

    @xamandaxgatewayx so when you take a certain drug it can either work as an agonists by enhancing the effect of a neurotransmitter, or it can work as an antagonist and prevent the neurotransmitter from working.

  65. xamandaxgatewayx December 24, 2011 at 12:08 pm #

    so when you take a certain drug it can either work as an agonists by enhancing the effect of a neurotransmitter, or it can work as an antagonist and prevent the neurotransmitter from working.

  66. xamandaxgatewayx December 24, 2011 at 5:05 pm #

    drugs can be examples of antagonists or agonists.

  67. xamandaxgatewayx December 24, 2011 at 5:08 pm #

    so when you take a certain drug it can either work as an agonists by enhancing the effect of a neurotransmitter, or it can work as an antagonist and prevent the neurotransmitter from working.

  68. wonderkid8991 December 30, 2011 at 1:00 pm #

    wow…i just got taught by Mike Tyson…i feel privileged..great vid

  69. wonderkid8991 December 30, 2011 at 6:00 pm #

    wow…i just got taught by Mike Tyson…i feel privileged..great vid

  70. dieurobotica January 2, 2012 at 2:56 pm #

    @msss432 hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  71. dieurobotica January 2, 2012 at 2:56 pm #

    hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  72. dieurobotica January 2, 2012 at 7:56 pm #

    hi, I only know about curare…I was taught that its an arrow poison…so, imagine one trying to shoot an animal and all of a sudden, ‘mistakenly’ shoots a person around…it will act… (thats the little I know about how it can get there)…

  73. dalodalo90 January 13, 2012 at 4:13 am #

    thank youuu

  74. dalodalo90 January 13, 2012 at 9:13 am #

    thank youuu

  75. Yorreh20 January 18, 2012 at 3:51 pm #

    @msss432
    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  76. Yorreh20 January 18, 2012 at 3:51 pm #

    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  77. Yorreh20 January 18, 2012 at 3:52 pm #

    @Yorreh20 I Meant “Agonist” in the example of succinyl-choline

  78. Yorreh20 January 18, 2012 at 3:52 pm #

    I Meant “Agonist” in the example of succinyl-choline

  79. Yorreh20 January 18, 2012 at 8:51 pm #

    Succinyl-choline (the antagonist) is a medication used in Healthcare, especially in anesthesiology (where people are sedated for surgery). It causes the muscles to relax so it’s easier to work with the body (i.e. intubation, cutting through muscle, opening the cuts)

    The antagonist is also a type of medication, lots of examples here. It also causes relaxation, but does so in a different manner (as explained in the video).

  80. Yorreh20 January 18, 2012 at 8:52 pm #

    I Meant “Agonist” in the example of succinyl-choline

  81. Michele January 22, 2012 at 8:20 pm #

    Leslie,
    Thank you so much for explaining and drawing out the differences between an agonist and an antagonist. You did an awesome job at breaking this concept down and now I can understand it completely! Sincerely,
    Michele

    • Lrsamuel January 22, 2012 at 9:29 pm #

      Thanks for the feedback Michele!

      All the best.

  82. lovejoy44ie January 29, 2012 at 7:32 am #

    Thank you so much, we are currently studying this in college, and to be honest i was very confused, but you made it very interesting, and i finally understand what is actually going.. Thank you again :)

  83. lovejoy44ie January 29, 2012 at 12:32 pm #

    Thank you so much, we are currently studying this in college, and to be honest i was very confused, but you made it very interesting, and i finally understand what is actually going.. Thank you again :)

  84. BondComputer007 February 23, 2012 at 9:46 pm #

    What is the difference between agonist and reuptake inhibitor?

  85. BondComputer007 February 23, 2012 at 9:47 pm #

    @BondComputer007

  86. liddlesez March 25, 2012 at 12:35 am #

    It’s my understanding is agonist and antagonists (same compounds can be both) depends on the effect they are going to have. A drug that might act as an antagoist for one compound might act as an antagonist. Some can be in the body, or administrated drugs via oral, iv and other routes of administration. I think that’s the best way to exam it. Have a read of some pharmcology text books :)

  87. liddlesez March 25, 2012 at 4:35 am #

    It’s my understanding is agonist and antagonists (same compounds can be both) depends on the effect they are going to have. A drug that might act as an antagoist for one compound might act as an antagonist. Some can be in the body, or administrated drugs via oral, iv and other routes of administration. I think that’s the best way to exam it. Have a read of some pharmcology text books :)

  88. brownthug69 April 14, 2012 at 4:59 pm #

    I would like to know this as well.

  89. brownthug69 April 14, 2012 at 8:59 pm #

    I would like to know this as well.

  90. pozionmynd June 13, 2012 at 12:00 pm #

    don’t confuse the nervous system with the muscular system hehe (inside joke)

  91. pozionmynd June 13, 2012 at 12:00 pm #

    don’t confuse the nervous system with the muscular system hehe (inside joke)

  92. Khaldon June 15, 2012 at 9:41 am #

    thank you very much I wish the best for this website and for the owner

  93. Biohazard826 September 4, 2012 at 9:31 pm #

    Thanks! This was very helpful to my Psychology study guide.

  94. zizi502 October 12, 2012 at 9:08 am #

    i want to know difference between types of antagonist ?

  95. Sarah CirrusBoutique October 23, 2012 at 8:22 pm #

    Brilliant again. These videos are really helping me get my head around this subject.

  96. Nikki Taylor October 25, 2012 at 1:26 pm #

    Thanks, you make these hard subjects easy to understand :)

  97. elaine joy gotardo November 21, 2012 at 12:06 pm #

    Can you please make a video regarding Chemical Antagonism sir?

  98. Sadiksha Adhikari December 3, 2012 at 4:53 pm #

    simple and easy to understand
    thank you

  99. fuser lock March 2, 2013 at 11:07 pm #

    Plain n simple…. Thank you!!!!:)

  100. kim kelly March 16, 2013 at 12:07 am #

    Very clear, can you please explain the functions of a receptor.

  101. Wawa Baptiste April 9, 2013 at 3:22 am #

    Thank you

  102. iSkyexx April 26, 2013 at 9:47 pm #

    Really simply and easy to understand! Thankyou so much, this is helping my Medications class :)

  103. Linda May 13, 2013 at 3:05 pm #

    Thank you Leslie, you are the best!!!! Btw, after watching some of your videos onhow action potential works in our brain. And other videos relating to the physiology of the brain I Aced my exam :)
    Thank you for all you do. I’m always watching and looking forward for more of your videos

    • Leslie Samuel May 13, 2013 at 3:54 pm #

      Woohoo, that’s so awesome. Congrats on Acing your exam. You rock!

  104. KARWAN JABBAR June 4, 2013 at 12:52 pm #

    how does an agonist drug work at synapse? Give an example

  105. Michael Xu July 3, 2013 at 3:41 pm #

    Thanks a lot!

  106. anna niko August 13, 2013 at 10:48 pm #

    thanks! that was so understandable!

  107. An Vũ September 14, 2013 at 7:07 pm #

    thanks. you make it so much easier to understand

  108. Phoenix Wings September 18, 2013 at 12:19 pm #

    thank god for youtube

  109. Sir Queef September 19, 2013 at 4:40 am #

    Black men don’t know pharmacology.

  110. Peehu Pandey September 28, 2013 at 3:13 am #

    learn to appreciate ,whatever the effort is ………..! No one is an absolute perfect.! right ….!

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    especially when you are not giving better than him………..! i would appreciate that.!

  112. Divya divs October 2, 2013 at 2:50 am #

    clear…and very good examples which r easy to undrstand……

  113. tamir sher October 25, 2013 at 5:25 pm #

    Thanks ! ! !

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  115. Darshna5 November 2, 2013 at 8:07 pm #

    thank you very much this helped so much