The horrible two-headed rat

I’m not impressed with this recent exercise in microsurgical technique to allow researchers to transplant the head of one rat to another rat’s body. In all honesty, I don’t see the point.

I’m going to put the discussion of this paper below the fold because it seems more an exercise in animal cruelty than anything else; I’ve included one figure illustrating the surgery, but it will be at thumbnail size and you’ll have to click on it to see it in all its gory vulgarity.

First, let’s get the justification out of the way. It’s a techniques paper to improve on methods for CSA. “CSA”, if you were curious, is short for “cephalosomatic anastomosis”, because obviously we’ve got to distance ourselves from what is being done with sciencey language, rather than just saying “head transplant”.

We thus developed several animal CSA models, including a full head transplant in mice, with the goal of testing both neuroprotective techniques (e.g., hypothermia) and antirejection immunological protocols. Here, we improve on the bicephalic preparations employed by past pioneers (see above).

This is not new. Of course you’ve got to concern yourself with rejection in any organ transplant; these concerns have already been worked on, and the head transplant is no different nor does this procedure add significantly to our body of knowledge. Another concern is ischemia and shock. If the switching of circulatory systems isn’t free of trauma or major disruptions in blood flow, you can cause serious organ damage. The brain is especially sensitive to this kind of problem, but again, these transitions and solutions are not new to surgeons — every time open heart surgery is performed, these changes are addressed.

So I’m at a loss. None of this is novel or necessary. It’s impressively delicate surgery, because I sure couldn’t stitch one teeny-tiny rat carotid to another rat’s, but the end result seems so futile and irrelevant.

Here’s what they did. Take one very small rat, the head donor, and one very large rat — 6 times larger than the donor — and anesthetize them. Open up the recipient rat’s neck and expose the jugular vein and carotid artery; tie them off (basically killing the recipient rat’s brain), and insert silicone tubes that travel through a peristaltic pump to help maintain a steady pressure, and then passes through a water bath that cools the blood to 31.5°C (hypothermia also helps protect the brain), and connect those to the axillary artery and vein of the donor rat.

Now the fun begins. Since oxygenated blood is now flowing from the host rat to the donor’s head, open up the donor’s chest, tie off the donor heart and lungs, and you can throw away the back half of the donor.

You can then stitch the donor rat’s head to the back of the neck of the host rat. Voila!

You may have noticed a bit of a cheat there. You use a host 6 times larger than the donor so, apparently, you have excess circulatory capacity and you can divert part of it to keep both animals “alive”. And it worked! For 6 hours, anyway.

In our experiment, the donor head was first connected to a rat’s blood supply, by peristaltic pumps, and only thereafter separated donor head from the donor body. In this state, the donor head was maintained for up to 6 hours, with no obvious abnormalities in the donor’s EEG or corneal reflexes. Following nociceptive stimuli, the donor head exhibited substantial movement.

Again, that last sentence is using a sciencey word to remove us all a bit from what they were doing. What it means is that when they did something painful to the donor head, it twitched and squirmed.

These are not surprising results. It’s exactly what I would expect would happen: maintain the blood supply to the head and you can do anything you want to the rest of the body, and the brain will still function. It doesn’t solve any of the major problems with head transplants. There is no restoration of nervous system connectivity. All they’ve shown is that you’ll be able to keep a disembodied head alive for a few hours if you dedicate the circulatory and respiratory systems of an entire decapitated corpse to pumping blood through it.

Not particularly useful. Unpleasant and grisly. A waste of rats for an irrelevant purpose.

If you must, here’s an illustration of the procedure.

Li PW, Zhao X, Zhao YL, Wang BJ, Song Y, Shen ZL, Jiang HJ, Jin H, Canavero S, Ren XP (2017) A cross-circulated bicephalic model of head transplantation. CNS Neurosci Ther. 2017 Apr 21. doi: 10.1111/cns.12700. [Epub ahead of print]


  1. OverlappingMagisteria says

    I have trouble keeping track of which one is the donor and which is the recipient, since: shouldn’t this be called a body transplant, not a head transplant? The mouse whose head stays alive is the one who would survive the operation. In my head, I can’t see that mouse as a donor. It got a new body.

    Any way… sounds weird and mostly pointless.

  2. evodevo says

    I’m puzzled … why did it only last 6 hours? Which system failed? Why kill the body donor’s head? It would be a lot cooler if it was a REAL two-headed rat, right? Sounds like they didn’t have a real hypothesis to test .. just screwing around?

  3. says

    They had to kill it, both to assess the histology of the brain and BECAUSE IT WOULD BE UNETHICAL TO TORMENT IT FURTHER. The body was reduced to a blood pump for a decapitated head. The head was stitched onto a rat-vegetable that could do nothing and was going to die soon anyway.

    Really, it was a ghastly experiment all around.

  4. The Mellow Monkey says

    Well. That was cruel and completely unnecessary.

    Rowan, yes. (Note: That link has a photograph of one of the dog experiments.)

  5. says

    That’s disgusting. All the more so because it was utterly pointless. Cruelty for cruelty’s sake is not science, and from what I can see, this was nothing more than “look what I can do!”

    I’ll give my crews some extra lovin’ tonight.

  6. Akira MacKenzie says

    Hasn’t the tragic tale of Rosey Grier and Ray Milland taught us not to tamper in such things?

  7. pacal says

    This sort of experiment is nothing new in the slightest. In the late 1950’s Soviet experimenters transplanted the heads and forearms of puppys onto living dogs. Actually quite grisly. THis was supposedly in aid of learning how to transplant organs into humans.

  8. Holms says

    ^ That 1950’s canine version was at least uncovering information that was new, and so advanced surgical transplant knowledge. I don’t see what this new version adds.

  9. DLC says

    They successfully transplanted Ray Milland’s head onto Rosy Grier’s body back in 1972 . . .

  10. wzrd1 says

    @#5 & #6, yeah, old rather novel experimentation that was rather horrific, begun anew, with no realistic objective, other than to achieve publication.

    While, I’ve frequently joked about needing a full body transplant, this is precisely the polar opposite of what I’d want.
    Killing another that I might live more comfortably and the punishment, lack of CNS function below the “replaced” region and likely, considering the reactions described, a lack of analgesia to the post-operative victim animal.

    This is fairly equal to an experimenter amputating both legs, then utilizing the various arteries and veins in the legs, to prove the validity of re-implanting his or her own head upon their own ass, grafting the arteries to the brain to the aorta and the veins to the inferior vena cava, then using a garden hose to connect the lower trachea to the lungs.
    One couldn’t even have that subject speak through their ass, but be in a hell of a lot of agony without analgesia, as any of my fellow creatures who have had major surgery could agree with.
    As PZ said, the creature could not survive, could not thrive, was in pain and needlessly so and proved that the 1950’s surgeon was superior in skills.
    Someone, call PETA.

    OT, but worrisome: Now, WTF is Trump doing now? It’s 1:30 AM here and B-52’s are taking off, which is unusual? Two *just* took off as I typed this.
    As their runway passes through residential areas, such takeoffs just don’t happen.
    Well, at least they don’t keep the nukes here, well, not since an incident in 2007.
    Rare in my life have I been left slack jawed in shock, that day, I truly was. *Every* rule, law and regulation on the handling of nuclear weapons was violated that day. I know that intimately well, as I started my military career in US Army nuclear weapons.
    Which is why I’m vehemently anti-nuclear weapons then and still today.

  11. Snarki, child of Loki says

    Sounds like a special episode of “Pinky and The Brain”.

    “What do you want to do today?”

    “Take over the world? I’m of two minds about that…”

  12. says

    Actually, I didn’t go over all the details, and it seems to have taken the death of two rats to support the decapitated head. One rat to provide the blood supply, a second rat to be finally stitched to the head, and the head.

  13. Callinectes says

    Grisly. Not as grisly as the YouTube video of a live mouse being fed to a snapping turtle, but that was just animal violence. This is creepily clinical.

  14. emergence says

    You ever notice how unethical, inhuman experiments are almost always scientifically useless?

  15. Rebecca Parker says

    I guess that explains why Canavero has moved to China to do his experiments.