Observations on central nervous system structures following the administration of a psychotomimetic substance.

)_ '. The incidental discovery that Lysergic-Safirc-Di_ithylamid (LSD) is a potent hallucinogenic substance has opened new prospectives in the study of some aspects of mental illnesses. The fact that a chemical compound, synthet_zed in the laboratory, has psychotomimetic effects and has a chemical configuration similar to that of a neurotransmitter -- serotonin -- present in the central nervous system, has stimulated several lines of research, from behaviour to electrophysiology and from neurochemistry to psychopbarmacology, regarding the effect of this drug on man and on experimental animals. It has been demonstrated that LSD has many sites of action in the central nervzus system (on the serotoninergic, nor-adrenergie, dopaminergic systems), but its mechanism of action is still poorly understood (for review see MARTIN and SLOANE, 1977).