Different drugs that activate the same serotonin receptor (5-HT2AR) can produce distinct patterns of gene expression in the brain, which correspond to different behavioral effects. The hallucinogens DOI and LSD triggered a head-twitch response in mice and produced similar changes in the somatosensory cortex transcriptome, while the nonhallucinogenic drug lisuride did not cause this behavior and generated a different transcriptome fingerprint. These effects were absent in mice lacking the 5-HT2AR, confirming the receptor's role. The findings suggest that drugs acting at the same receptor can induce unique cellular response patterns in the living brain, detectable through transcriptome analysis.
Hallucinogenic drugs like LSD, mescaline, and psilocybin all bind strongly to the serotonin 5-HT(2A) receptor. Drugs that affect metabotropic glutamate 2/3 (mGlu2/3) receptors can alter the cellular and behavioral effects of hallucinogens. In mice, chronic treatment (21 days) with the mGlu2/3 receptor antagonist LY341495 (1.5 mg/kg) reduced the hallucinogenic-like effects of LSD (0.24 mg/kg). This treatment decreased binding of a radiolabeled tracer to 5-HT(2A) receptors in the somatosensory cortex of normal mice, but not in mice lacking the mGlu2 receptor. It also reduced head-twitch behavior and the expression of certain genes (c-fos, egr-1, egr-2) that are normally triggered by hallucinogenic drugs. These results suggest that repeatedly blocking mGlu2 receptors dampens the 5-HT(2A) receptor-mediated effects of LSD.