Both S-ketamine (an NMDA antagonist) and DMT (a 5HT2A agonist) reduced mismatch negativity (MMN) and impaired performance on a continuous performance test in healthy volunteers, but the effects differed. S-ketamine produced a more pronounced overall reduction in MMN and specifically affected the frontal source of MMN, while DMT did not. These distinct neurocognitive profiles suggest that the two classes of hallucinogens model different aspects of psychosis.
Two modifications of an HPLC-ED method for measuring psilocin, the active metabolite of psilocybin, in human plasma were developed and compared. One used liquid-liquid extraction (LLE) and the other automated on-line solid-phase extraction (on-line SPE). Both methods had a limit of quantitation of 10 ng/ml psilocin and showed no significant difference in standard deviation (LLE 1.82%, on-line SPE 1.13%) or analytical results. On-line SPE required less manual effort, smaller plasma volumes (400 microl versus 2 ml), and achieved nearly 100% recovery of psilocin (LLE 88%). Both methods were rapid, simple, and reliable, and were successfully used to quantify psilocin in plasma samples from healthy volunteers after oral administration of 0.2 mg psilocybin per kg body mass.