Therapeutic usefulness of hallucinogenic drugs as a function of their chemical structure.

D-lysergic acid diethylamide (LSD) displays (1) the phenylethylamine pattern present in mescaline, cyclazocine and catecholamines and (2) the 4-substituted tryptamine structure of psilocybin which is a serotonin analog. Hence (a) Naloxone--a blocker of the LSD-like side effects of cyclazocine--should (and does) block effects of LSD, and (b) cross-tolerance may be present between LSD and cyclazocine but not between mescaline and psilocybin. Even though LSD binds subcortically, its effect on regional perfusion of the brain and, presumably, function is primarily cortical and, since the perfusion shifts evoked by psilocybin are confined to subcortical regions, we assume that other compounds with the phenylethylamine structure such as mescaline, also may selectively affect cortical activity.