OPEN Foundation

H. Hansen

A Single Dose of Psilocybin Increases Synaptic Density and Decreases 5-HT 2A Receptor Density in the Pig Brain

February 6, 2022 / Depression, Mushrooms / Psilocybin, Neuroscience, Papers / Leave a Comment / By / , , , , , ,

Abstract

A single dose of psilocybin, a psychedelic and serotonin 2A receptor (5-HT2AR) agonist, may be associated with antidepressant effects. The mechanism behind its antidepressive action is unknown but could be linked to increased synaptogenesis and down-regulation of cerebral 5-HT2AR. Here, we investigate if a single psychedelic dose of psilocybin changes synaptic vesicle protein 2A (SV2A) and 5-HT2AR density in the pig brain. Twenty-four awake pigs received either 0.08 mg/kg psilocybin or saline intravenously. Twelve pigs (n = 6/intervention) were euthanized one day post-injection, while the remaining twelve pigs were euthanized seven days post-injection (n = 6/intervention). We performed autoradiography on hippocampus and prefrontal cortex (PFC) sections with [3H]UCB-J (SV2A), [3H]MDL100907 (5-HT2AR antagonist) and [3H]Cimbi-36 (5-HT2AR agonist). One day post psilocybin injection, we observed 4.42% higher hippocampal SV2A density and lowered hippocampal and PFC 5-HT2AR density (-15.21% to -50.19%). These differences were statistically significant in the hippocampus for all radioligands and in the PFC for [3H]Cimbi-36 only. Seven days post-intervention, there was still significantly higher SV2A density in the hippocampus (+9.24%) and the PFC (+6.10%), whereas there were no longer any differences in 5-HT2AR density. Our findings suggest that psilocybin causes increased persistent synaptogenesis and an acute decrease in 5-HT2AR density, which may play a role in psilocybin’s antidepressive effects.

Raval, N. R., Johansen, A., Donovan, L. L., Ros, N. F., Ozenne, B., Hansen, H. D., & Knudsen, G. M. (2021). A Single Dose of Psilocybin Increases Synaptic Density and Decreases 5-HT2A Receptor Density in the Pig Brain. International journal of molecular sciences, 22(2), 835. https://doi.org/10.3390/ijms22020835

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Effects of a single dose of psilocybin on behaviour, brain 5-HT 2A receptor occupancy and gene expression in the pig

January 21, 2022 / Mushrooms / Psilocybin, Neuroscience, Papers, Psychopharmacology / Leave a Comment / By / , , , , , , , , ,

Abstract

Psilocybin has in some studies shown promise as treatment of major depressive disorder and psilocybin therapy was in 2019 twice designated as breakthrough therapy by the U.S. Food and Drug Administration (FDA). A very particular feature is that ingestion of just a single dose of psilocybin is associated with lasting changes in personality and mood. The underlying molecular mechanism behind its effect is, however, unknown. In a translational pig model, we here present the effects of a single dose of psilocybin on pig behaviour, receptor occupancy and gene expression in the brain. An acute i.v. injection of 0.08 mg/kg psilocybin to awake female pigs induced characteristic behavioural changes in terms of headshakes, scratching and rubbing, lasting around 20 min. A similar dose was associated with a cerebral 5-HT2A receptor occupancy of 67%, as determined by positron emission tomography, and plasma psilocin levels were comparable to what in humans is associated with an intense psychedelic experience. We found that 19 genes were differentially expressed in prefrontal cortex one day after psilocybin injection, and 3 genes after 1 week. Gene Set Enrichment Analysis demonstrated that multiple immunological pathways were regulated 1 week after psilocybin exposure. This provides a framework for future investigations of the lasting molecular mechanisms induced by a single dose of psilocybin. In the light of an ongoing debate as to whether psilocybin is a safe treatment for depression and other mental illnesses, it is reassuring that our data suggest that any effects on gene expression are very modest.

Donovan, L. L., Johansen, J. V., Ros, N. F., Jaberi, E., Linnet, K., Johansen, S. S., Ozenne, B., Issazadeh-Navikas, S., Hansen, H. D., & Knudsen, G. M. (2021). Effects of a single dose of psilocybin on behaviour, brain 5-HT2A receptor occupancy and gene expression in the pig. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 42, 1–11. https://doi.org/10.1016/j.euroneuro.2020.11.013

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Classics in Neuroimaging: The Serotonergic 2A Receptor System-from Discovery to Modern Molecular Imaging

May 15, 2018 / LSD, Neuroscience, Other subjects, Papers, Psychopharmacology, Publications / By / , , , , ,

Abstract

Already in 1953, Woolley and Shaw speculated that serotonin could be involved in a range of central nervous system (CNS) disorders. Lysergic acid diethylamide (LSD) displayed an important role in this respect. It was used not only to antagonize biological effects of serotonin and to study the system itself, but also to identify serotonergic subtype receptors. The 5-HT2A receptor was discovered in the 1970s and identified as the responsible receptor mediating psychedelic effects of LSD. The development of positron emission tomography (PET) allowed to study this receptor system in vivo. Parameters such as abundance of 5-HT2A neuroreceptors or receptor occupancy can be determined using PET. As such, the development of 5-HT2A receptor tracers started immediately after the introduction of PET in the mid-1970s. In this Viewpoint, we provide a historical overview from the discovery of serotonin to the identification of the 5-HT2A receptor subtype and the subsequent development of 5-HT2A receptor subtype specific PET tracers over the last four decades. We emphasize the interplay between pharmacology, medicinal chemistry, radiochemistry, and nuclear medicine that is important while developing a PET tracer. Moreover, we highlight selected examples applying 5-HT2A receptor PET tracers within neurological diseases and drug occupancy studies.
T. L’Estrade, E., Hansen, H. D., Erlandsson, M., Ohlsson, T. G., Knudsen, G. M., & Herth, M. M. (2018). Classics in Neuroimaging: The Serotonergic 2A Receptor System—from Discovery to Modern Molecular Imaging. 10.1021/acschemneuro.8b00176
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30 April - Q&A with Rick Strassman

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