The 5-HT2A receptor plays a major role in mediating the effects of the hallucinogens DMT and DiPT. A 5-HT2A receptor inverse agonist fully blocked the discriminative stimulus effects of DMT but only partially blocked those of DiPT. A 5-HT2C receptor antagonist partially attenuated DiPT's effects but minimally affected DMT. An mGluR2/3 agonist produced potent but partial blockade of DMT's effects, while an mGluR2/3 antagonist facilitated the effects of both compounds. Both DMT and DiPT induced head twitches, with DiPT producing more, and these were blocked by a 5-HT2A receptor inverse agonist. DiPT acted as a low-potency full agonist at the 5-HT2C receptor in vitro. The findings suggest that 5-HT2C and mGluR2 receptors modulate the effects of these tryptamine hallucinogens to some degree.
In mice genetically modified to express human CYP2D6 (Tg-CYP2D6) and wild-type mice, the psychedelic 5-MeO-DMT produced similar rates of learning a drug discrimination task. Bufotenine did not substitute for 5-MeO-DMT, while its lipid-soluble analog acetylbufotenine produced intermediate substitution. Combining harmaline with 5-MeO-DMT significantly increased drug-appropriate responding in both mouse types, indicating harmaline enhances 5-MeO-DMT's stimulus effects. Harmaline alone also produced significant 5-MeO-DMT-appropriate responding in Tg-CYP2D6 mice, suggesting metabolic interactions. No differences between wild-type and Tg-CYP2D6 mice were found in acquisition or responses to bufotenine and acetylbufotenine.