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Neurotransmitter Notes: Serotonin + Oxytocin

April 29, 2022

10 year old me: I can't wait to grow up, I bet it would be amazing. Adult me: a picture of a cartoon face making the pspsps sound at a chemical diagram of serotonin the way one would call a cat.

 

Take two of our Neurotransmitter Notes! If you are in the midst of finals season like me, maybe you want something to cheer you up. I might not be able to make your neurons fire off serotonin or oxytocin, but maybe learning about them will help you produce your own! Without further ado, let’s set the tone with serotonin…

 

“Am I going crazy

Consuming me lately

And I’m well

I’m over it

Not where I’ve been

It’s where I’m going

Looking for my vibe

Wanna bathe myself in serotonin”

 

Serotonin- Courtney Govan

 

After dopamine, serotonin might just be the second most well known neurotransmitter. And like dopamine, it has effects beyond making you happier: it could be better described as a mood regulator that can also affect your sleep, digestion, and wound healing (Serotonin, n.d.).

 

But before you buy those serotonin gummies off the internet, be careful! Too much serotonin can lead to serotonin syndrome, This alliterative ailment can cause vomiting, headache, rapid heart rate, and muscle twitches (Dunkin, n.d.). In this situation, you really can have too much of a good thing. But what about the opposite?

 

A lot of people being treated for depression know about serotonin in the context of “the thing I need more of”. This perception is described in girl in red’s Serotonin:

 

“I’m running low on serotonin

Chemical imbalance got me twisting things

Stabilize with medicine

But there’s no depth to these feelings

Dig deep, can’t hide

From the corners of my mind

I’m terrified of what’s inside”

 

Serotonin- girl in red

 

Indeed, depression is linked to lower activity of neurons that use serotonin. One of the most common antidepressants prescribed nowadays are the selective-serotonin reuptake inhibitors (SSRIs). The medicine girl in red describes is likely an SSRI, which works by preventing serotonin from being taken up by neurons after it is released into a synapse (the junction between neurons where neurotransmitters transfer a signal from one neuron to the next). This increases synaptic serotonin levels. Then, like if you were to increase the number of balls in a pinball machine, the serotonin is more likely to bind to a receptor on the other side, activating the next neuron. Boom–more activity!

an image showing the process by which ssris prevent serotonin from leaving the synapse.
A diagram showing the function of SSRIs (SSRIs, 2010)

 

And to round out our discussion of the three “happy chemicals” people know about, let’s talk about oxytocin! Now, oxytocin is technically a hormone and not a neurotransmitter (do you remember the difference from my last article?).  Compared to dopamine and serotonin, oxytocin is perhaps the one most related to gettin’ hot and heavy in the public eye. Just take a look at these lyrics from Billie Eilish:

 

“Can’t take it back once it’s been set in motion

You know I need you for the oxytocin

If you find it hard to swallow

I can loosen up your collar

‘Cause as long as you’re still breathing

Don’t you even think of leaving”

 

Oxytocin- Billie Eilish

 

Here, she really shows the burst of excitement that can stem from oxytocin. Oxytocin makes us feel more connected to the people around us. However, it is not just released among lovers–it’s actually a key player in childbirth and nursing (Watson, 2021). It is also released during exercise, listening to music, and any type of physical contact. How touching!

 

That’s all I have for you all today. Take some personal time to relax and hug a friend (or partner)! We’ll get through this period together.

 

Check out this playlist with the tunes mentioned in this article, as well as some other neuroscience related songs! (Note: please be aware that some songs in this playlist may have explicit lyrics)

 

References

Dunkin, M. A. (n.d.). Serotonin syndrome. WebMD. Retrieved April 27, 2022, from https://www.webmd.com/depression/guide/serotonin-syndrome-causes-symptoms-treatments

Serotonin: What is it, function & levels. (n.d.). Cleveland Clinic. Retrieved April 27, 2022, from https://my.clevelandclinic.org/health/articles/22572-serotonin

Skabreus. (2021, June 12). I can’t wait to grow up [Reddit Post]. R/Memes. www.reddit.com/r/memes/comments/ny9ds6/i_cant_wait_to_grow_up/

SSRIs. (2010, June 30). HOPES Huntington’s Disease Information. https://hopes.stanford.edu/ssris/

Watson, S. (2021, July 20). Oxytocin: The love hormone. Harvard Health. https://www.health.harvard.edu/mind-and-mood/oxytocin-the-love-hormone

 

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I'm a 3rd year neuroscience major interested in the intersection of science and art! I also like to share my experiences as someone studying an uncommon major.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.