Fainting: The Link Between the Heart and Brain

For some, fainting can be a daily struggle, an anticipation of the next bout of lost

consciousness. Scientists have begun to recognize that there appears to be a

connection between the brain and heart that leads to fainting spells and there seems to

be an added genetic component for theformation of the heart. The Bezold-Jarisch reflex

(BJR) is when cardiac inhibitor receptors are activated leading to dilations of blood

vessels, hypotension, a slow heart rate, and eventually syncope or fainting. This reflex

was found to occur due to activation of the specific type of vagal sensory neurons called

NPY2R.


Lovelace et al. did a study on mice, where they discovered a connection between

vagal neurons, vNAS stalled heartbeats, and BJR. In order to discover this connection

they manipulated the specific neurons, NPY2R. By manipulating these neurons, the

mice went from their normal activities to immediately fainting. However, when these

neurons were removed, the mice stopped fainting all together. To excite the neurons, a

method called optogenetics was used. Optogenetics is when light stimulates certain

channels and pumps the target neurons, which consequently activates the neurons.

This testing also revealed that there appears to be restricted blood flow to the brain

during these activations, which furthers the likelihood of fainting. Restricted blood flow is

due to a decreased cardiac output and increases in the volume of blood in the left

ventricle. In the discussion, they come to the conclusion that BJR is activated by

NPY2R VSNs that act as substrates for BJR. This conclusion basically states that

NPY2R VSNs causes BJR to occur, which then leads to syncope.


With a better understanding of the neural-heart connection that leads to syncope,

the next steps are to determine if it is plausible to remove NPY2R neurons in the human

brain, without causing damage. The cardiac inhibitor receptors for BJR are activated by

NPY2R VSNs, it’s substrate. If the substrate were to be removed, then the cardiac

inhibitor receptors don’t activate cardiac inhibition. This discovery is important because

it gives hope to those who might be scared to go out their own door due to unexpected

fainting.


Posted by: Alexis Carson (8)


Lovelace JW, Ma J, Yadav S, Chhabria K, Shen H, Pang Z, Qi T, Sehgal R, Zhang Y,

Bali T, et al. 2023 Nov 1. Vagal sensory neurons mediate the Bezold–Jarisch reflex and

induce syncope. Nature.:1–10. doi:https://doi.org/10.1038/s41586-023-06680-7.

[accessed 2023 Nov 5]. https://www.nature.com/articles/s41586-023-06680-7#Sec9.

Comments

  1. Madeline GouldNovember 15, 2023 at 9:42 PM

    Hi Alexis! This post is very interesting! I have always been intrigued by fainting and its causes. I have never fainted, and have never known if there are factors that can contribute to someone fainting or being more likely to. The neuron manipulation and removal is very interesting because if it possible to remove the neuron from someone who frequently faints, it could potentially channge their life for the better.

    ReplyDelete
  2. AnonymousNovember 16, 2023 at 9:05 AM

    Hi Alexis! This is super interesting! I have a bunch of friends that faint constantly and I've always wondered what causes that. It's really interesting that this substrate can just be removed from the body and the problem would be solved! I wonder if that would have any negative impacts on the body at all?
    - Nicole M.

    ReplyDelete
  3. AnonymousNovember 17, 2023 at 7:12 AM

    Hi Alexis!
    This newfound understanding of the neural-heart connection in syncope opens up potential avenues for treatment. The removal of NPY2R neurons in the human brain, if it can be done safely without causing damage, could prevent the activation of cardiac inhibitor receptors, thereby preventing fainting. This discovery offers hope for those affected by frequent fainting spells, as it suggests the possibility of leading a more normal and worry-free life without the fear of sudden syncope.This newfound understanding of the neural-heart connection provides potential avenues for future research and potential treatments to address the fear and unpredictability associated with fainting. This study also makes me wonder what potential complications could occur when NPY2R neurons are removed.
    -Carla B

    ReplyDelete
  4. Megan WinklerNovember 19, 2023 at 6:37 AM

    Hey Alexis - great post! It's sad how many people have to live every day worrying about syncope but its uplifting to know there is active research trying to alleviate this struggle for these people. It's fascinating how far we've come in neurobiology that we can pinpoint specific problematic neurons and remove them or other treatments of the sort. Thanks for sharing!

    ReplyDelete
  5. Jill GobbiNovember 20, 2023 at 9:24 AM

    Hey Alexis! As someone who has always suffered with ocular migraine's and bouts of syncope, this topic is very close to home for me. I think it is so interesting how one nerve can do so much to the human body. I also wonder if certain neurons can be removed from the brain without causing further damage. It reminds me of the man that got a railroad spike in the brain but could still function almost normally. It's crazy to me how sometimes we don't know how crucial a part of the brain is to survival until you remove.

    ReplyDelete

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