Table 1.

Summary of included studies.

	Ketamine	Psychedelics
Agents	Racemic ketamine (n = 65), R-ketamine (n = 5), S-ketamine (n = 5)	DMT (n = 2), DOI (n = 7), ibogaine/noribogaine (n = 2), LSD (n = 3), psilocyn/psilocybin (n = 3)
In vivo or in vitro	In vivo (n = 63), in vitro (n = 14)	In vivo (n = 8), in vitro (n = 6)
Subjects	Rats/rat cells (n = 33), mice/mouse cells (n = 40), humans/human cells (n = 4), non-human primates (n = 1)	Rats/rat cells (n = 9), mice/mouse cells (n = 3), pigs (n = 1)
Brain regions	Cortical (ACC, dlPFC, FC, IL, mPFC, OFC, PFC, PrL, vmPFC; n = 55), hippocampal (CA1, CA3, DG; n = 45), striatal (NAc shell and core, dorsal striatum; n = 11)	Cortical (FC, mPFC, IL, PFC, PrL, OFC; n = 11), hippocampal (CA1, CA3, DG; n = 4)
Synaptic markers	PSD-95 (n = 36), SV2A (n = 1), SYN (n = 20), SYP (n = 3), SYT (n = 1), structural dendritic measures (n = 35)	PSD-95 (n = 3), SV2A (n = 1), SYN (n = 1), structural dendritic measures (n = 11)
Overall outcome summarya	↑ (≈50%), — (≈27%), ↓ (≈23%)	↑ (≈47%), — (≈40%), ↓ (≈13%)

The total counts differ from 84, because some of the studies used both in vivo and in vitro approaches, and/or investigate more than one agent and/or more than one type of animal. DMT, dimethyltryptamine; DOI, 2,5-Dimethoxy-4-Iodoamphetamine; LSD, lysergic acid diethylamide; ↑, increase; —, no change; ↓, decrease; ACC, anterior cingulate cortex; CA1 and CA3, hippocampal subregion cornu ammonis; DG, hippocampal subregion dentate gyrus; FC, frontal cortex; NAc, nucleus accumbens; dlPFC, dorsolateral prefrontal cortex; IL, infralimbic; mPFC, medial prefrontal cortex; PFC, prefrontal cortex; vmPFC, ventromedial prefrontal cortex; PrL, prelimbic; OFC, orbitofrontal cortex; SYN, synapsin-1; SYP, synaptophysin-1; SYT, synaptotagmin-1; SV2A, synaptic vesicle glycoprotein 2A.

^aApproximate percentages within included studies.