Preclinical Comparison of DMT and 5-MeO-DMT Reveals Behavioral Dissociation, Distinct TrkB Activation and Differential Plasticity Profiles

N, N-dimethyltryptamine (DMT) and 5-methoxy-N, N-dimethyltryptamine (5-MeO-DMT) are structurally related tryptamine psychedelics with emerging therapeutic potential, yet their comparative acute pharmacology and longer-term neuroplastic effects remain incompletely defined. Here we show that DMT produces a bell-shaped dose–response curve in the mouse head-twitch response (HTR) assay, whereas 5-MeO-DMT elicits a monotonic increase. Selective antagonism at 5-HT2A or 5-HT1D receptors, or agonism at 5-HT1A, robustly attenuates HTR for both compounds without abolishing their ability to reduce marble burying, a screening assay for OCD-like behavior. Acutely, both agents elevate TrkB phosphorylation in a region-specific manner, with broader engagement by DMT across default-mode-network and hippocampal territories. Twelve days after a single dose, both compounds increase synaptic proteins (PSD-95, synaptophysin; SV2A for DMT), while DMT uniquely lowers hippocampal BDNF and reprograms frontal-cortex glutathione and energy metabolism. These findings demonstrate that acute hallucinogenic-like activity and selected therapeutic-like behavioral and plasticity outcomes can be pharmacologically dissociated, informing the rational design of more tolerable, scalable psychedelic-based treatments.