A COMPARISON OF N,N-DIMETHYLTRYPTAMINE, HARMALINE, AND SELECTED CONGENERS IN RATS TRAINED WITH LSD AS A DISCRIMINATIVE STIMULUS

1. A series of N-substituted tryptamines was compared with a series of beta-carbolines in rats trained to discriminate LSD (0.1 mg/kg) from saline. 2. Intermediate levels of substitution were elicited by MDMT ( 76.4%), DMT (77.9%), and DET (48.7%). 6-F-DET produced 41.3% LSD-appro priate responding at a dose of 6.0 mg/kg but only 4 of 8 subjects comp leted the test session thus precluding statistical analysis. Bufotenin e (25.8%) also failed to substitute. Although none of the tryptamines substituted completely for LSD, the pattern of substitution is consona nt with what is known of their activity in humans. MDMT, DMT, and DET are well established in the literature as hallucinogens but the same c annot be said for 6-F-DET and bufotenine. 3. Of the beta-carbolines te sted, none substituted for LSD completely and only harmane elicited in termediate substitution (49.5%). No significant generalization of the LSD stimulus to 6-methoxyharmalan, harmaline, or THBC was observed. Th us, in contrast to the tryptamines, scant ability to substitute for LS D was observed in the beta-carbolines tested. 4. Taken together, the p resent data indicate that the representative tryptamines employed in t he present study exhibit greater similarity to the LSD stimulus than d o representative beta-carbolines. The receptor interactions responsibl e for these differences remain to be determined.