ObjectiveIt has been proposed that the thalamocortical system is an important site of action of hallucinogenic drugs and an essential component of the neural correlates of consciousness. Hallucinogenic drugs such as LSD can be used to induce profoundly altered states of consciousness, and it is thus of interest to test the effects of these drugs on this system.Method100 μg LSD was administrated orally to 20 healthy participants prior to fMRI assessment. Whole brain thalamic functional connectivity was measured using ROI‐to‐ROI and ROI‐to‐voxel approaches. Correlation analyses were used to explore relationships between thalamic connectivity to regions involved in auditory and visual hallucinations and subjective ratings on auditory and visual drug effects.ResultsLSD caused significant alterations in all dimensions of the 5D‐ASC scale and significantly increased thalamic functional connectivity to various cortical regions. Furthermore, LSD‐induced functional connectivity measures between the thalamus and the right fusiform gyrus and insula correlated significantly with subjective auditory and visual drug effects.ConclusionHallucinogenic drug effects might be provoked by facilitations of cortical excitability via thalamocortical interactions. Our findings have implications for the understanding of the mechanism of action of hallucinogenic drugs and provide further insight into the role of the 5‐HT 2A‐receptor in altered states of consciousness.
Lysergic acid diethylamide (LSD) induces profound changes in various mental domains, including perception, self-awareness and emotions. We used functional magnetic resonance imaging (fMRI) to investigate the acute effects of LSD on the neural substrate of emotional processing in humans. Using a double-blind, randomised, cross-over study design, placebo or 100 μg LSD were orally administered to 20 healthy subjects before the fMRI scan, taking into account the subjective and pharmacological peak effects of LSD. The plasma levels of LSD were determined immediately before and after the scan. The study (including the a priori-defined study end point) was registered at ClinicalTrials.gov before study start (NCT02308969). The administration of LSD reduced reactivity of the left amygdala and the right medial prefrontal cortex relative to placebo during the presentation of fearful faces (P<0.05, family-wise error). Notably, there was a significant negative correlation between LSD-induced amygdala response to fearful stimuli and the LSD-induced subjective drug effects (P<0.05). These data suggest that acute administration of LSD modulates the engagement of brain regions that mediate emotional processing.
Psilocybin, the principal indole alkaloid of Psilocybe mushrooms, is currently undergoing clinical trials as a medication against treatment‐resistant depression and major depressive disorder. The psilocybin supply for pharmaceutical purposes is met by synthetic chemistry. We replaced the problematic phosphorylation step during synthesis with the mushroom kinase PsiK. This enzyme was biochemically characterized and used to produce one gram of psilocybin from psilocin within 20 minutes. We also describe a pilot‐scale protocol for recombinant PsiK that yielded 150 mg enzyme in active and soluble form. Our work consolidates the simplicity of tryptamine chemistry with the specificity and selectivity of enzymatic catalysis and helps provide access to an important drug at potentially reasonable cost.
We report the identification of ω-N-methyl-4-hydroxytryptamine (norpsilocin, 1) from the carpophores of the hallucinogenic mushroom Psilocybe cubensis. The structure was elucidated by 1D and 2D NMR spectroscopy and high-resolution mass spectrometry. Norpsilocin has not previously been reported as a natural product. It likely represents the actual psychotropic agent liberated from its 4-phosphate ester derivative, the known natural product baeocystin. We further present a simple and artifact-free extraction method that prevents dephosphorylation and therefore helps reflect the naturally occurring metabolic profile of Psilocybe mushrooms in subsequent analyses.
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