Interactions of partial LSD analogs with behavioral disrupting effects of LSD and DMT in the rat

Adult male Holtzman rats were trained to barpress on a schedule whereby every fourth press earned a reward of 0.01 ml of sugar-sweetened milk (FR₄). After an i.p. injecton of LSD (0.1 mg/kg) or DMT (3.2 or 10 mg/kg) such barpressing is abolished completely and resumed, usually within an hour, at a rate near the preinjection control rate of pressing. It continues at a steady, uninterrupted pace until animals are removed from the operant chamber one-half hour later. A series of N,N-diethylnipecotamide derivatives were synthesized and tested for their ability to modify the disruptive effect of these hallucinogens. N,N-diethylbutyramide (DBA) and 1-methyl-1,2,5,6-tetrahydropyridine-3-(N,N-diethylcarboxamide) (THPC) were also tested. Pretreatment with a single i.p. injection of any of these compounds (5-40 mg/kg) either had no effect on or else prolonged the duration of hallucinogen-induced cessation of barpressing.