A single dose of d-LSD, a potent serotonergic agonist, increased preference for novel objects in young and adult rats several days after treatment, but did not increase preference in old animals unless followed by a 6-day exposure to enriched environment, which rescued novelty preference to young levels. Mass spectrometry-based proteomics in human brain organoids treated with d-LSD showed upregulation of proteins from the presynaptic active zone. A computational model of synaptic connectivity in the hippocampus and prefrontal cortex suggests that d-LSD enhances novelty preference by combining local synaptic changes in mnemonic and executive regions with alterations of long-range synapses, and that better pattern separation within enriched environment explains its synergy with d-LSD in rescuing novelty preference in old animals. These results advance the use of d-LSD in cognitive enhancement.
Harmine, a β-carboline found in the ayahuasca vine Banisteriopsis caapi, upregulates proteins in human brain organoids that are involved in synaptic vesicle cycling, cytoskeleton-dependent transport, cell cycle, glucose transporter-4 translocation, and neurotrophin signaling. Treatment with harmine also increased levels of Akt and phosphorylated CREB after 24 hours. These findings point to cellular and molecular pathways that may explain harmine's potential neuroprotective effects, which have been suggested by previous animal studies to include anti-inflammatory and antioxidant activities. The work advances understanding of how harmine might contribute to the antidepressant effects observed with ayahuasca.