Imperial College London

Dr. Tobias Buchborn, Dipl. Psych.

Faculty of MedicineDepartment of Brain Sciences

Honorary Research Fellow



+44 (0)20 7594 3205t.buchborn




Burlington DanesHammersmith Campus





Publication Type

10 results found

Kaertner L, Steinborn M, Kettner H, Spriggs M, Roseman L, Buchborn T, Timmermann Slater C, Erritzoe D, Carhart-Harris Ret al., 2021, Positive expectations predict improved mental-health outcomes linked to psychedelic microdosing, Scientific Reports, Vol: 11, ISSN: 2045-2322

Psychedelic microdosing describes the ingestion of near-threshold perceptible doses of classicpsychedelic substances. Anecdotal reports and observational studies suggest that microdosingmay promote positive mood and well-being, but recent placebo-controlled studies failed to fndcompelling evidence for this. The present study collected web-based mental health and related datausing a prospective (before, during and after) design. Individuals planning a weekly microdosingregimen completed surveys at strategic timepoints, spanning a core four-week test period. Eightyone participants completed the primary study endpoint. Results revealed increased self-reportedpsychological well-being, emotional stability and reductions in state anxiety and depressivesymptoms at the four-week primary endpoint, plus increases in psychological resilience, socialconnectedness, agreeableness, nature relatedness and aspects of psychological fexibility. However,positive expectancy scores at baseline predicted subsequent improvements in well-being, suggestiveof a signifcant placebo response. This study highlights a role for positive expectancy in predictingpositive outcomes following psychedelic microdosing and cautions against zealous inferences on itsputative therapeutic value.

Journal article

Buchborn T, Lyons T, Song C, Feilding A, Knöpfel Tet al., 2020, The serotonin 2A receptor agonist 25CN-NBOH increases murine heart rate and neck-arterial blood flow in a temperature-dependent manner., Journal of Psychopharmacology, Vol: 34, Pages: 786-794, ISSN: 0269-8811

BACKGROUND: Serotonin 2A receptors, the molecular target of psychedelics, are expressed by neuronal and vascular cells, both of which might contribute to brain haemodynamic characteristics for the psychedelic state. AIM: Aiming for a systemic understanding of psychedelic vasoactivity, here we investigated the effect of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine - a new-generation agonist with superior serotonin 2A receptor selectivity - on brain-supplying neck-arterial blood flow. METHODS: We recorded core body temperature and employed non-invasive, collar-sensor based pulse oximetry in anesthetised mice to extract parameters of local blood perfusion, oxygen saturation, heart and respiration rate. Hypothesising an overlap between serotonergic pulse- and thermoregulation, recordings were done under physiological and elevated pad temperatures. RESULTS: N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine (1.5 mg/kg, subcutaneous) significantly increased the frequency of heart beats accompanied by a slight elevation of neck-arterial blood flow. Increasing the animal-supporting heat-pad temperature from 37°C to 41°C enhanced the drug's effect on blood flow while counteracting tachycardia. Additionally, N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine promoted bradypnea, which, like tachycardia, quickly reversed at the elevated pad temperature. The interrelatedness of N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine's respiro-cardiovascular effects and thermoregulation was further corroborated by the drug selectively increasing the core body temperature at the elevated pad temperature. Arterial oxygen saturation was not affected by N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine at either temperature. CONCLUSIONS: Our findings imply that selective serotonin 2A receptor activation modulates systemic cardiovascular functioning in orchestration with thermoregulation and with immediate relevance to brain-imminent

Journal article

Buchborn T, Lyons T, Knopfel T, 2018, Tolerance and Tachyphylaxis to Head Twitches Induced by the 5-HT2A Agonist 25CN-NBOH in Mice, Frontiers in Pharmacology, Vol: 9, ISSN: 1663-9812

The serotonin (5-HT) 2A receptor is the primary molecular target of serotonergic hallucinogens, which trigger large-scale perturbations of the cortex. Our understanding of how 5-HT2A activation may cause the effects of hallucinogens has been hampered by the receptor unselectivity of most of the drugs of this class. Here we used 25CN-NBOH (N-(2-hydroxybenzyl)-2,5-dimethoxy-4-cyanophenylethylamine), a newly developed selective 5-HT2A agonist, and tested it with regard to the head-twitch-response (HTR) model of 5-HT2A activity and effects on locomotion. 25CN-NBOH evoked HTRs with an inverted u-shape-like dose-response curve and highest efficacy at 1.5 mg/kg, i.p. HTR occurrence peaked within 5 min after agonist injection, and exponentially decreased to half-maximal frequency at ~11 min. Thorough habituation to the experimental procedures (including handling, saline injection, and exposure to the observational boxes 1 day before the experiment) facilitated the animals' response to 25CN-NBOH. 25CN-NBOH (1.5 mg/kg, i.p.) induced HTRs were blocked by the 5-HT2A antagonist ketanserin (0.75 mg/kg, 30 min pre), but not by the 5-HT2C antagonist SB-242084 (0.5 mg/kg, i.p., 30 min pre). SB-242084 instead slightly increased the number of HTRs occurring at a 3.0-mg/kg dose of the agonist. Apart from HTR induction, 25CN-NBOH also modestly increased locomotor activity of the mice. Repeated once-per-day injections (1.5 mg/kg, i.p.) led to reduced occurrence of 25CN-NBOH induced HTRs. This intermediate tolerance was augmented when a second (higher) dose of the drug (3.0 mg/kg) was interspersed. Short-interval tolerance (i.e., tachyphylaxis) was observed when the drug was injected twice at intervals of 1.0 and 1.5 h at either dose tested (1.5 mg/kg and 0.75 mg/kg, respectively). Inducing ketanserin-sensitive HTRs, which are dependent on environmental valences and which show signs of tachyphylaxis and tolerance, 25CN-NBOH shares striking features common to serotonergic hallucinogens. Gi

Journal article

Buchborn T, Grecksch G, Dieterich D, Hoellt Vet al., 2016, Tolerance to Lysergic Acid Diethylamide: Overview, Correlates, and Clinical Implication, Neuropathology of Drug Addictions and Substance Misuse. Volume 2: Stimulants, Club and Dissociative Drugs, Hallucinogens, Steroids, Inhalants and International Aspects., Editors: Preedy, Pages: 846-858

The first reports on tolerance to the serotonergic hallucinogen lysergic acid diethylamide (LSD) were published half a century ago, yet hitherto, a systematic review on this topic is not available. In this chapter, we discuss tolerance to LSD with regard to its psychedelic and somatic effects in humans, as well as selected behaviors in animals. In humans, mental tolerance to LSD substantially manifests 24 h after its first administration and reaches a maximum by around the fourth day. Once established, tolerance cannot be overcome even if the initial dose is quadrupled. Mental tolerance to LSD generalizes to psilocybin and mescaline but not to tetrahydrocannabinol or amphetamine. As to LSD’s somatic effects, mental tolerance most reliably is accompanied by tolerance to mydriasis. Five days of abstinence is sufficient for tolerance to be reversed; symptoms of withdrawal are not encountered. In animals, LSD-induced shaking behavior, limb flicking, and hallucinogenic pausing are undermined by tolerance, too; the first-mentioned behaviors, for instance, are subject to tachyphylaxis. Mechanistically, pharmacodynamic adaptations of serotonin 5-HT2A and/or (downstream) glutamate receptors are likely to account for tolerance; a learning-related precipitation, however, has also been described. The rapid onset of mental tolerance probably is a main reason LSD generally is not taken on an everyday basis by humans. Given its rapid reversal, on the other hand, a once-per-week abuse cannot be excluded.

Book chapter

Buchborn T, Schroeder H, Koch T, Kahl E, Dieterich DC, Grecksch G, Hoellt Vet al., 2016, Differential tolerance to lysergic acid diethylamide (LSD) and dimethyltryptamine (DMT) - A matter of serotonin (5-HT) 2A receptor downregulation?, 82nd Annual Meeting of the German-Society-for-Exerimental-and-Clinical-Pharmacology-and-Toxicology (DGPT) / 18th Annual Meeting of the Network-Clinical-Pharmacology-Germany (VKliPha), Publisher: SPRINGER, Pages: S63-S63, ISSN: 0028-1298

Conference paper

Buchborn T, Schroeder H, Koch T, Kahl E, Dieterich DC, Grecksch G, Hoellt Vet al., 2016, Differential tolerance to lysergic acid diethylamide (LSD) and dimethyltryptamine (DMT) - A matter of serotonin (5-HT) 2A receptor downregulation?, Publisher: SPRINGER, Pages: 63-63, ISSN: 0028-1298

Conference paper

Buchborn T, Schroeder H, Dieterich DC, Grecksch G, Hoellt Vet al., 2015, Tolerance to LSD and DOB induced shaking behaviour: Differential adaptations of frontocortical 5-HT2A and glutamate receptor binding sites, BEHAVIOURAL BRAIN RESEARCH, Vol: 281, Pages: 62-68, ISSN: 0166-4328

Journal article

Buchborn T, Schroeder H, Hoellt V, Grecksch Get al., 2014, Repeated lysergic acid diethylamide in an animal model of depression: Normalisation of learning behaviour and hippocampal serotonin 5-HT2 signalling, JOURNAL OF PSYCHOPHARMACOLOGY, Vol: 28, Pages: 545-552, ISSN: 0269-8811

Journal article

Buchborn T, Kahl E, Hoellt V, Koch Tet al., 2012, Agonist-selective internalization of the human 5-HT2A receptor, Publisher: SPRINGER, Pages: 17-17, ISSN: 0028-1298

Conference paper

Buchborn T, Kahl E, Hoellt V, Koch Tet al., 2012, Agonist-selective internalization of the human 5-HT2A receptor, 78th Annual Congress of the German-Society-for-Experimental-and-Clinical-Pharmacology-and-Toxicology (DGPT), Publisher: SPRINGER, Pages: 17-17, ISSN: 0028-1298

Conference paper

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