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Episode Summary: Dr. Alex Kwan discusses how psychedelics like ketamine and psilocybin induce rapid neuroplastic changes in the brain, particularly in the prefrontal cortex, contrasting their effects with traditional antidepressants like SSRIs, and exploring their potential for treating depression and chronic pain through structural and functional brain alterations.

About the guest: Alex Kwan, PhD, is an associate professor of biomedical engineering at Cornell University. His lab employs advanced imaging to study how psychedelics and other drugs affect the mammalian brain.

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Key Discussion Points:

* Ketamine & psilocybin rapidly increase dendritic spine density in the prefrontal cortex, enhancing neural connections within days, unlike SSRIs, which take weeks.

* These drugs show sustained neuroplastic changes in mice, lasting weeks to months after a single dose, suggesting long-term brain rewiring.

* Serotonin 2A receptor is critical for psilocybin’s neuroplastic effects, as precise genetic knockouts in adult mice eliminate spine growth.

* Unlike ketamine, psilocybin activates the insula, a brain region linked to chronic pain processing, hinting at new therapeutic potential.

* Both drugs induce similar gene expression patterns in areas like the prefrontal cortex and amygdala, but differ in specific regions like the insula.

Reference paper:

* Study: Psilocybin’s lasting action requires pyramidal cell types and 5-HT2A receptors

Related episode:

* M&M #30: Psilocybin, Ketamine, Neuroplasticity & Imaging the Brain | Alex Kwan

*Not medical advice.

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* Episode transcript below.

Episode Chapters:

00:00:00 Intro00:04:32 Cerebral Cortex Structure00:09:00 Excitatory vs. Inhibitory Neurons00:14:20 Depression & Neuroplasticity00:19:19 SSRI Effects & Limitations00:24:34 Ketamine & Psilocybin Rapid Effects00:30:00 Dendritic Spine Plasticity00:36:01 Serotonin 2A Receptor Debate00:41:32 Ketamine vs. Psilocybin Mechanisms00:46:08 Measuring Psychedelic Effects in Mice00:52:13 Head Twitch Response Limitations00:57:10 Serotonin 2A Receptor Knockout Results01:03:19 c-Fos Mapping Insights01:09:28 Future Research Directions

Full AI-generated transcript below. Beware of typos & mistranslations!