More than 200 species of mushroom contain the psychoactive compound psilocybin – the hallucinogenic substance in so-called ‘magic mushrooms’.
When psilocybin is metabolised in the bodies of mammals, the chemical psilocin is created. Psilocin structurally resembles serotonin receptors and can bind to serotonin receptors. This can then influence behaviour and emotions, including aggression, appetite, mood and memory.
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Now, in a study published in Frontiers in Behavioral Neuroscience, researchers from Canada have discovered that low doses of psilocybin reduce aggressive behaviours in a particular type of fish.
The scientists used lab-bred mangrove rivulus fish in their experiments, as they commonly demonstrate aggressive behaviours such as swimming bursts.
“Swimming bursts are high‑energy attack behaviours that represent an escalation of aggression towards other fish without making physical contact,” explains senior author Suzie Currie, a biologist at The University of British Columbia.
“Other types of aggressive behaviours, like head‑on displays, are more about communication and social assessment and require very little energy.”
Calmer waters?
To test the effects of psilocybin, the researchers used three different lines of fish. Firstly, the focal fish were introduced to a water tank containing stimulus fish to measure their baseline behaviour.
The fish were separated by a barrier through which the fish could see and smell (but not reach) each other. After an adjustment period, the barrier was removed and interaction monitored.
Twenty-four hours later, the same focal fish were introduced to a water tank in which psilocybin was dissolved. After exposure for 20 minutes, the focal fish were added into the tank occupied by the same stimulus fish the day before (carrying out the same adjustment period as before).
This was repeated using a different line of fish that had not been dosed with psilocybin.
After the adjustment period, the researchers observed that when the fish were dosed with psilocybin, they showed significantly lower levels of activity and performed fewer swimming bursts.
There was no significant alteration in the frequency of more social behaviours such as head-on displays. No differences were observed in the control group.
“Psilocybin’s calming effect appears to selectively reduce energetically costly, escalated behaviours while lower‑energy social display behaviours remained largely unchanged,” says the study’s first author Dayna Forsyth, a research associate and former MSc student at Acadia University in Nova Scotia.
“This suggests that this compound can selectively dampen escalated social conflict, rather than shutting down behaviour altogether.”
The psilocybin did influence activity levels of the fish, with the dosed fish spending less time moving around the tank than the line of control fish.
Further research
The findings could help inform further research by clarifying which aspects of social behaviour are most sensitive to psilocybin. However, the team warns that these results from fish cannot be directly applied to humans.
“Future studies can build on this work to explore how psilocybin alters neural signalling, which serotonin pathways are involved, and why some aspects of social behaviour are affected while others are not,” concludes Currie.
“These are questions that are difficult or impossible to answer directly in humans.”
Read the full paper: The magic of mushrooms: Psilocybin influences behaviour in the mangrove rivulus fish, Kryptolebias marmoratus
Top image: a mangrove rivulus fish. Credit: Cardet co6cs, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons
