The Unbearable Lightness of Dying?

Death has been everywhere in the news media since the announcement of Bin Laden's demise on Sunday. How this historic event will affect global terrorism is unknown; perhaps the most important news of all was of the treasure trove of computers and files found in Bin Laden's luxury "compound."

With this event in mind, I came across today one of the strangest (some might say creepy) studies I have ever read - a biochemical study on death and dying. Researchers have found that death and dying can invoke euphoria and something like an "unbearable lightness." Seriously.

In a study published in Neuroscience Letters, German scientists reported:

serotonin levels significantly increased during the process of dying, while the EEG went down to a zero-line, indicating no neuronal activity

The neurotransmitter serotonin is known to be associated with a feeling of "well being" and of happiness. How curious - a feeling of "well being" during the process of dying.


Serotonin, or 5-hydroxytryptamine (5-HT)

Here's their data, using anesthetized rats:


How did they do the study?

six adult male Wistar rats were deeply anesthetized (chloral hydrate 400 mg/kg) and placed in a stereotaxic apparatus. A microdialysis probe (membrane 0.6 Ã 2 mm) was placed in the primary auditory cortex (AP-4,3; ML 7,0; DV 5,2). After insertion, the first dialysate was sampled after 2 h. Samples of extracellular dialysate were collected every 20 min for at least 2 h and analyzed using high-performance liquid chromatography (HPLC) with an electrochemical detector. Quantification of serotonin concentrations was based on the chromatographic peak height using the external standard method. After cessation of breathing during this time, dialysate collection and EEG monitoring were continued. For EEG recordings, a tripolar stainless steel screw-electrode was used to record neuronal activity of the primary auditory cortex epidurally (AP-5.6, ML 7,0 related to bregma). Reference electrode was placed on the skull anterior to the frontal cortex. Electrical brain signals were transmitted to high-impedance preamplifiers. The EEG was filtered between 3 and 1000 Hz and sampled at 500 Hz. EEG was recorded and analyzed by commercial software (Brain Vision Recorder, Brain Vision Analyzer).

The conclusion:

Similar to the endogenous opiods, which may prevent the organism from pain during dying, serotonin as a key neurotransmitter in mood modulation possibly induces a well-balanced and pleasant mood-state to make dying easier for the individual organism.

From a more psychological point of view, the increase of neurotransmitters such as endorphins or serotonin during dying might be the neurobiological correlate of so-called near death experiences with, for example, an extremely elevated mood during e.g. cardiac arrest.

I suppose that there's good news in this study; that we have a "protection mechanism" that supports good feelings as we approach the end. I would rather wait for that final rush though.

More like this

Well, why not? I like the idea of feeling good, as things close down, and I go into that last adventure. A nice farewell, and better at least than the excruciating (sp) pain so many cancer patients feel.

Maybe nature is telling us we should provide this benefit on demand to those who need it.

Wondering if there's any evolutive advantage gained from this process. What do you think?

@ Daniel #2

That was a good one, you actually had me thinking about it for a second.

PS: That was supposed to be a joke, right?

You can't equate serotonin with a positive mood. It's a transmitter that corresponds to a multitude of processes at the mental level (including, but certainly not limited to, aggression). In fact, its upregulation does not translate into improved mood, as can be seen through upregulating it via SSRI antidepressants: neither depressed or non-depressed people show a mood effect, although depressed people can display mood changes after a month of continuous upregulation or so.

That being said, it's release may be telling of the nature of the cells that release the compound instead of its effect on mind or behavior. Not everything neurobiological has a psychological counterpart.

And actually Daniel makes a pretty good point, whether he realised it or not.

"mood modulation possibly induces a well-balanced and pleasant mood-state to make dying easier for the individual organism."

There is no way that could have been selected for, as this so-called adaptation does not lead to an increase in differential reproduction. It may be the by-effect of some other mechanism, but the proposed "function" makes no sense.

There are many different elements to the near death experience of which only one is feeling good surrounded by love. Actually the brain has nothing to do with the experience since at the time it is clinically dead. The research on the experience has shown that consciousness continues to live after the brain and body are clinically dead. I will leave a link to the research into veridical near death experiences.

To the commenters mentioning that there could be no evolutionary advantage: people sometimes survive near-death experiences. An organism that faced a life-threatening situation and survived might be more risk-taking regarding that situation in the future, or display any of the other personality changes people have after near-death experiences.

Risk-taking, of course, is variably selected depending on circumstances, but! One is more likely to survive an only apparently life-threatening experience, and so survivors of such experiences with a feeling of well-being might be less likely to fear engaging them in the future.

By Inflection (not verified) on 05 May 2011 #permalink

Vincent @5: There are plenty of ways this mechanism could be selected for.

Way #1: Individuals occasionally survive near-death experiences. Being calm instead of in frantic agony may improve those odds. Those survivors could then pass on their genes, making it directly selected for.

Way #2: An individual who is mortally wounded by a predator could still manage to get away. The predator might then kill a relative of the mortally wounded individual (since dinner got away), while the first individual dies too. The first individual won't reproduce themselves, but succumbing to the wound would be a form of kin selection in this case.

Way #3: Individuals dying under very stressful conditions may be detrimental to other members of the same species. This could be for lots of reasons; if death was clearly excruciating, then individuals around the dying individual could be stressed out by the screaming (and we know stress is bad for you). Alternatively, a noisy dying individual may attract the attention of predators that would also threaten the relatives. Or, relatives might flee from the dying individual, denying themselves access to nearby shelter or resources for no good reason. Again, kin selection would favor the calm death in this scenario.

Way #4 (which you mention): Some other feature of the neurobiology was the target of selection, but also (as an unselected side-effect or constraint) results in serotonin flooding the neurons of dying individuals. So the near-death experience is a spandrel.

Hi everyone,

@scott #3: actually no, it was not meant to be a joke, although I see now that it could... :)
I asked because i really didn't see any obvious answer, but the comments #5, #7, and #8 provide very interesting ideas.

Thank you all.

#4... That was my first thought and it seems to obvious. Equating increased serotonin levels with euphoria is just not accurate. Serotonin syndrome anyone? First of all, serotonin is not just a 'feel good' neurotransmitter, and as Vincent pointed out, SSRI's don't necessarily make people happy or less depressed. Many people report feeling numb. I agree an increase serotonin could be a function of neuronal death, as in release, and lack of uptake.