Low doses of psychedelic drug erases conditioned fear in mice

by Anne Delotto Baier
Psilocybin, which exerts psychoactive effects, has been isolated from certain mushrooms.

(Medical Xpress)—Low doses of a psychedelic drug erased the conditioned fear response in mice, suggesting that the agent may be a treatment for post-traumatic stress disorder and related conditions, a new study by University of South Florida researchers found.

The unexpected finding was made by a USF team studying the effects of the compound on the birth of new neurons in the brain and on learning and short-term . Their study appeared online June 2 in the journal Experimental Brain Research, in advance of print publication.

Psilocybin belongs to a class of compounds that stimulate select serotonin receptors in the brain. It occurs naturally in certain mushrooms that have been used for thousands of years by non-Western cultures in their religious ceremonies.

While past studies indicate psilocybin may alter perception and thinking and elevate mood, the psychoactive substance rarely causes hallucinations in the sense of seeing or hearing things that are not there, particularly in lower to moderate doses.

There has been recent renewed interest in medicine to explore the potential clinical benefit of psilocybin, MDMA and some other through carefully monitored, evidence-based research.

"Researchers want to find out if, at lower doses, these drugs could be safe and effective additions to psychotherapy for treatment-resistant psychiatric disorders or adjunct treatments for certain neurological conditions," said Juan Sanchez-Ramos, MD, PhD, professor of neurology and Helen Ellis Endowed Chair for Parkinson's Disease Research at the USF Health Morsani College of Medicine.

Dr. Sanchez-Ramos and his colleagues wondered about psilocybin's role in the formation of short-term memories, since the agent binds to a serotonin receptor in the hippocampus, a region of the brain that gives rise to new neurons. Lead author for this study was neuroscientist Briony Catlow, a former PhD student in Dr. Sanchez-Ramos' USF laboratory who has since joined the Lieber Institute for Brain Development, a translational neuroscience research center located in the Johns Hopkins Bioscience Park.

The USF researchers investigated how psilocybin affected the formation of memories in using a classical conditioning experiment. They expected that psilocybin might help the mice learn more quickly to associate a neutral stimulus with an unpleasant environmental cue.

To test the hypothesis, they played an auditory tone, followed by a silent pause before delivering a brief shock similar to static electricity. The mice eventually learned to link the tone with the shock and would freeze, a fear response, whenever they heard the sound.

Later in the study, the researchers played the sound without shocking the mice after each silent pause. They assessed how many times it took for the mice to resume their normal movements, without freezing in anticipation of the shock.

Regardless of the doses administered, neither psilocybin nor ketanserin, a serotonin inhibitor, made a difference in how quickly the mice learned the conditioned fear response. However, mice receiving low doses of psilocybin lost their fearful response to the sound associated with the unpleasant shock significantly more quickly than mice getting either ketanserin or saline (control group). In addition, only low doses of psilocybin tended to increase the growth of neurons in the hippocampus.

"Psilocybin enhanced forgetting of the unpleasant memory associated with the tone," Dr. Sanchez-Ramos said. "The mice more quickly dissociated the shock from the stimulus that triggered the and resumed their normal behavior."

The result suggests that psilocybin or similar compounds may be useful in treating or related conditions in which environmental cues trigger debilitating behavior like anxiety or addiction, Dr. Sanchez-Ramos said.

More information: "Effects of psilocybin on hippocampal neurogenesis and extinction of trace fear conditioning," Briony J. Catlow, Shijie Song, Daniel A. Paredes, Cheryl L. Kirstein and Juan Sanchez-Ramos; Experimental Brain Research, published online June 2, 2013; DOI 10.1007/s00221-013-3579-0

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VendicarE
3 / 5 (6) Jul 16, 2013
If applicable to people, this would seem to be a treatment for Republican disease. No longer would the fools be able to be managed by their political handlers through fear.

Now we only need to focus on boosting Republican IQ by 50 to 100 percent, and they would be nearly fully functional people.

MandoZink
5 / 5 (3) Jul 16, 2013
This property that many psychoactive substances possess has been well known to large numbers of humans for a long, long time. The ability of the experience to also increase empathy has a profound effect on civility and personal well-being.

One study I read recently was this from Johns Hopkins:
http://www.hopkin...y_change

For the casual therapeutic event I recommend creating a positive setting first: good friends, nice environment (possible outdoors) and uplifting mellow music. And maybe a beer.
zorro6204
3.3 / 5 (3) Jul 16, 2013
Could work. I recall after about a 10X overdose of acid, other things suddenly seemed a lot less scary!
eric_in_chicago
5 / 5 (2) Jul 16, 2013
those shrooms pictured are not p.c. s

those look like honey shrooms which are a common edible.

i have never tried them.

o.k. maybe they are...hmmmm who can tell without up close inspection.
Twin
3 / 5 (4) Jul 16, 2013
@VandicarE your comments are becoming as boring and predictable as the vacuum mech guy. belittle, name call, then change the subject to conservative hate.
I think you, sometimes, have interesting insights but, you seldom share them anymore.
PhotonX
5 / 5 (2) Jul 17, 2013
those shrooms pictured are not p.c. s

those look like honey shrooms which are a common edible.

i have never tried them.

o.k. maybe they are...hmmmm who can tell without up close inspection.
Drop the picture onto Google Images and you get a match for "psilocybin mushrooms", but not a specific identification. In my literature I see several species that this could be a match for. Particularly Psilocybe mexicana and Psilocybe semilanceata, though there are others. Hard to tell with just a single image to go by.
lolwut1
1 / 5 (1) Jul 17, 2013
If applicable to people, this would seem to be a treatment for Republican disease. No longer would the fools be able to be managed by their political handlers through fear.

Now we only need to focus on boosting Republican IQ by 50 to 100 percent, and they would be nearly fully functional people.



That's a great theory. Too bad 50-100% wouldn't be enough to make you functional in society.
wookieecookies
5 / 5 (1) Jul 17, 2013
The fact that they could potentially erase "conditioned fear" speaks volumes about their illegality..
Media Miller
5 / 5 (1) Jul 18, 2013
It's a health care business, This line of natural product substitution is way worse than corporate synthetic chemicals running out of patent protection. If you could see the movie without buying a ticket, you wouldn't need to buy a ticket each time. The time that heals all wounds cannot be delivered by the business.
fizzlemcshizzle
5 / 5 (1) Jul 20, 2013
wookie, and consider the converse, there are chemicals that have special legal protection, that are administered without consent where the agents of the government are insulated from any resulting damage. Drugs that were specifically developed by studying animal fear conditioning with the criteria of preventing the animal from overcoming fear conditioning, now frequently labeled Anti-psychotics or Neuroleptics.
Sinister1811
1 / 5 (2) Jul 21, 2013
Psilocybin would be a breakthrough treatment in social anxiety or other anxiety disorders.
Zenmaster
not rated yet Jul 21, 2013
"If applicable to people, this would seem to be a treatment for Republican disease."
That would only treat half the problem.