A Single Dose of LSD Does Not Alter Gene Expression of the Serotonin 2A Receptor Gene (HTR2A) or Early Growth Response Genes (EGR1-3) in Healthy Subjects

Regarding the phenomenon of rapid tolerance after repeated use of LSD, this double-blind study (2017, n=15) found that a single dose of LSD (100 μg) did not alter gene expression of the serotonin (5-HT) 2A receptor gene.

Abstract

“Rationale: Renewed interest has been seen in the use of lysergic acid diethylamide (LSD) in psychiatric research and practice. The repeated use of LSD leads to tolerance that is believed to result from serotonin (5-HT) 5-HT_2A receptor downregulation. In rats, daily LSD administration for 4 days decreased frontal cortex 5-HT_2A receptor binding. Additionally, a single dose of LSD acutely increased expression of the early growth response genes EGR1 and EGR2 in rat and mouse brains through 5-HT_2A receptor stimulation. No human data on the effects of LSD on gene expression has been reported. Therefore, we investigated the effects of single-dose LSD administration on the expression of the 5-HT_2A receptor gene (HTR2A) and EGR1-3 genes.

Methods: mRNA expression levels were analyzed in whole blood as a peripheral biomarker in 15 healthy subjects before and 1.5 and 24 h after the administration of LSD (100 μg) and placebo in a randomized, double-blind, placebo-controlled, cross-over study.

Results: LSD did not alter the expression of the HTR2A or EGR1-3 genes 1.5 and 24 h after administration compared with placebo.

Conclusion: No changes were observed in the gene expression of LSD’s primary target receptor gene or genes that are implicated in its downstream effects. Remaining unclear is whether chronic LSD administration alters gene expression in humans.”

Authors: Patrick C. Dolder, Edna Grünblatt, Felix Müller, Stefan J. Borgwardt & Matthias E. Liechti

Summary

INTRODUCTION

Lysergic acid diethylamide (LSD) is a psychoactive substance that transiently alters mind and perception. Modern experimental studies in humans have reported LSD’s subjective, autonomic, and endocrine effects.

LSD’s pharmacological effects remain unclear, including the phenomenon of tolerance to LSD, which is believed to result from serotonin 5-HT2A receptor downregulation. The 5-HT2A receptor is a partial agonist of LSD, and the 5-HT2A receptor antagonist ketanserin completely prevents all perceptual and mind-altering effects of LSD in humans. Rats develop tolerance to the behavioral effects of LSD by decreasing 5-HT2A receptor binding in the frontal cortex, but no effects of acute LSD were found on 5-HT2A receptor mRNA expression in the prefrontal cortex, hippocampus, or midbrain. Instead, adaptations in glutamate receptors were observed. LSD increased the expression of several genes in the rat prefrontal cortex, including EGR2, and also increased the expression of EGR2 and EGR1 in the mouse cortex via 5-HT2A receptor stimulation.

Despite renewed interest in the clinical use of LSD, no human studies have been performed on the effects of LSD on gene expression.

Acute changes in gene expression cannot be determined in healthy human brain tissue, but mRNA level changes in blood for candidate genes including EGR and HTR2A can cautiously be used as peripheral markers of transcription alterations in the CNS in response to interventions or to characterize patient groups.

Study Design

The study used a double-blind, placebo-controlled, cross-over design and was approved by the Ethics Committee of Northwestern Switzerland. All subjects provided written informed consent and were paid for their participation.

Participants

Twenty-four healthy subjects were studied. Blood samples were taken from 15 participants, 7 men and 8 women, with a mean age of 28.5 years, mean weight of 68 kg, and mean BMI of 22.0 kg/m2.

Study Procedures

The experimental sessions were conducted in a standard hospital patient room. LSD or placebo was administered at 9:00 AM, and a standardized lunch and dinner were served at 1:30 and 5.30 PM, respectively.

Gene Expression

Blood samples were collected before and 1.5 and 24 h after drug administration. Total RNA was prepared using the PAXgeneTM Blood RNA Kit 50, and the RNA quality was measured using Experion RNA chips. Quantitative real-time polymerase chain reaction (PCR) was performed on the HTR2A, EGR1, EGR2, and EGR3 genes and six additional reference genes. The PCR conditions are listed in Table 1.

PCR reactions were run on a CFX384 device (BioRad, Hercules, CA, United States) according to the manufacturer’s manual, and the PCR efficiency was determined using LinRegPCR 2016.0 software. The analysis of gene expression and normalization with the most stable reference genes was conducted using qBasePlus 3.0 software.

Plasma Concentrations of LSD

Blood samples were collected before and 1, 2, 3, 4, 6, 8, 10, 12, 16, and 24 h after LSD administration. LSD concentrations in plasma were determined using liquid-chromatography-tandem mass-spectrometry.

Statistics

The statistical analyses were performed using Statistica 12 software (StatSoft, Tulsa, OK, United States). The results were analyzed using paired t-tests and ANOVAs with time (0, 1.5, and 24 h) as a within-subject factor followed by Tukey post hoc test.

RESULTS

The expression patterns of HTR2A, EGR1, EGR2, and EGR3 genes were unchanged 1.5 and 24 h after the administration of LSD compared with placebo. Sex did not moderate the effects of LSD or placebo on gene expression.

DISCUSSION

The present study found that acute LSD administration did not alter the expression of the HTR2A and EGR1-3 genes in humans using peripheral blood cells as peripheral biomarker possibly reflecting central gene expression. However, it is possible that LSD alters gene expression in the brain and not in blood.

Acute pharmacological tolerance to repeated LSD administration in humans is reportedly beginning with the second daily dose of LSD, and complete tolerance develops within 3 – 4 days of repeated LSD administration. However, no acute tolerance was observed in the participants in the present study.

A recent study showed that LSD dissociates very slowly from the 5-HT2A receptor, and that its high potency and long effect duration may be linked to a unique receptor interaction. However, the presence of LSD in the body sufficiently accounted for the duration of its subjective effects.

LIMITATIONS

The present study has several limitations, including using only an acute single dose of LSD, assessing gene expression only at 1.5 and 24 h after LSD administration, and focusing solely on human blood cells as a peripheral biomarker of the central nervous system.