Behavioral effects of α,α,β,β-tetradeutero-5-MeO-DMT in rats: comparison with 5-MeO-DMT administered in combination with a monoamine oxidase inhibitor.
BACKGROUND
Ayahuasca is a psychoactive tea prepared from a combination of plants that contain a hallucinogenic tryptamine and monoamine oxidase inhibitors (MAOIs). Behavioral pattern monitor (BPM) experiments demonstrated that the combination of 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and a behaviorally inactive dose of an MAO(A) inhibitor such as harmaline or clorgyline induces biphasic effects on locomotor activity in rats, initially reducing locomotion and then increasing activity as time progresses.


OBJECTIVE
The present study investigated whether the biphasic locomotor profile induced by the combination of 5-MeO-DMT and an MAOI is a consequence of a reduction in the rate of 5-MeO-DMT metabolism. This hypothesis was tested using a deuterated derivative of 5-MeO-DMT (α,α,β,β-tetradeutero-5-MeO-DMT) that is resistant to metabolism by MAO.


RESULTS
Confirming our previous findings, 1.0 mg/kg 5-MeO-DMT (s.c.) had biphasic effects on locomotor activity in rats pretreated with a behaviorally inactive dose of the nonselective MAOI pargyline (10 mg/kg). Administration of 5-MeO-DMT alone, even at doses greater than 1.0 mg/kg, produced only reductions in locomotor activity. Although low doses of α,α,β,β-tetradeutero-5-MeO-DMT (0.3 and 1.0 mg/kg, s.c.) produced only hypoactivity in the BPM, a dose of 3.0 mg/kg induced a biphasic locomotor profile similar to that produced by the combination of 5-MeO-DMT and an MAOI. Receptor binding studies demonstrated that deuterium substitution had little effect on the affinity of 5-MeO-DMT for a wide variety of neurotransmitter binding sites.


CONCLUSIONS
The finding with α,α,β,β-tetradeutero-5-MeO-DMT indicates that the hyperactivity induced by 5-MeO-DMT after MAO inhibition is a consequence of reduced metabolism of 5-MeO-DMT, leading to prolonged occupation of central serotonin receptors. These results demonstrate that deuterated tryptamines may be useful in behavioral and pharmacological studies to mimic the effects of tryptamine/MAOI combinations.
Department of Psychiatry, University of California San Diego, La Jolla, CA, USA. ahalbers@ucsd.edu
Adam L
AL
Halberstadt
David E
DE
Nichols
Mark A
MA
Geyer
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002027:Bufotenin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D003903:Deuterium / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D008297:Male; D008732:Methoxydimethyltryptamines / Q000008:administration & dosage / Q000494:pharmacology*; D008996:Monoamine Oxidase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D010293:Pargyline / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000378:metabolism
D008732:Methoxydimethyltryptamines; D008996:Monoamine Oxidase Inhibitors; D011985:Receptors, Serotonin; C575196:alpha,alpha,beta,beta-tetradeutero-5-methoxy-N,N-dimethyltryptamine; D002027:Bufotenin; D010293:Pargyline; D003903:Deuterium