Antagonism of the effects of the hallucinogen DOM and the purported 5-HT agonist quipazine by 5-HT2 antagonists.

Rats trained to discriminate 1.0 mg/kg of 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) from saline in a two-lever operant choice task were administered doses of mescaline, LSD, 5-methoxy-N,N-dimethyltryptamine (5-OMe DMT), quipazine, TFMPP and RU-24969. The DOM-stimulus generalized to the three hallucinogenic agents and to quipazine, but not to the purported serotonin agonists TFMPP or RU-24969. Pretreatment of the animals with the 5-HT2 antagonists ketanserin and pirenperone antagonized the effect produced by DOM. Pirenperone also blocked DOM-stimulus generalization to mescaline, LSD, 5-OMe DMT and quipazine. The results of this study suggest that the discriminative stimulus effects of DOM, the three hallucinogenic agents to which DOM-stimulus generalization occurred, and quipazine, may involve those sub-populations of serotonin receptors that are labeled by tritiated ketanserin (i.e. 5-HT2 sites).