Low doses of psychedelic psilocybin mushrooms have been found to aid in removing a condition fear response in lab mice. The Lieber Institute for Brain Development conducted the study to find out how psilocybin affected fear and anxiety.

Psilocybin and Fear in Mice – Methodology Day 1


Mice were injected with varying doses (0.1, 0.5, 1.0 and 1.5 mg/kg) of psilocybin, 1.0 mg/kg of ketanserin (a drug that acts oppositely on the receptor which binds psilocybin), or a saline control.

– Twenty-four hours later, the animals were placed in a testing chamber and conditioned to fear a 15-second audio cue.

– The mice heard the cue, and after 30 seconds, received very brief electric shocks delivered through the chamber floor. Each mouse underwent ten trials, each separated by 210 seconds.

After ten trials, all of the animal subjects froze in fear after the start of the 15-second audio.

Psilocybin and Fear in Mice – Methodology Day 2


The next day, the mice were placed in the chamber again and underwent the same process. Except this time, the shock was left out. The goal here was to effectively retrain the mice to not fear the audio cue and disassociate it with the shock.

– The researchers found that after only three trials, mice treated with low doses of psilocybin (0.1 and 0.5 mg/kg) no longer froze after hearing the audio cue.

– But mice injected with higher doses of psilocybin or ketanserin didn’t stop freezing until the tenth trial.

– Mice that were injected with a saline control still froze in fear after ten trials.

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The head of the research team, Dr. Briony Catlow thinks the fear removing effect of psilocybin might have something to do with the mushroom’s ability to modify and control neural circuitry.

“Memory, learning, and the ability to relearn that a once threatening stimuli is no longer a danger absolutely depends on the ability of the brain to alter its connections,” Catlow told Real Clear Science.

“We believe that neuroplasticity plays a critical role in psilocybin accelerating fear extinction.

“It is highly possible that in the future we will continue these studies since many interesting questions have come up from these experiments. The hope is that we can extend the findings to humans in clinical trials,” Catlow told RCScience.

Low Doses of Psilocybin Help Extinguish Conditioned Fear | Real Clear Science


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