| Summary: | After a general introduction and a short historical background of psychopharmacology, the relevant literature on mescaline is reviewed. Some of the problems concerning experimental design in psychopharmalogical research are considered. A series of experiments was conducted to investigate the effect of mescaline on behaviour in the hooded rat. Several analogues were also studied in a CAR (shuttle box) situation and in an activity (open field) situation. It became apparent that the experimental parameters involved were important since the findings obtained with a given drug differed according to the circumstances. The results showed that mescaline (25 mg/kg) had a biphasic (inhibition followed by excitation) effect where the shuttle box was concerned, but only an excitatory effect in the open field. 3,4-dimethoxypherylethylamine was found to be mainly depressive in action in both experiments, whereas N:N-dimethosqyphenylethylamine apparently acted as a stimulant. Other analogies of mescaline were also tested in the CAR situation and the possible implications of the findings are discussed. It was decided to study mescaline further in order to see whether a specific drug profile existed. The tests used were conflict and the perception of depth the possible presence of ataxia and peripheral effects were also checked. In a conflict situation, a biphasic effect similar to that of the CAR experiment was seen. Perception of depth, as judged by the visual cliff and the hole test, was affected, but not biphasically; the animals appeared fearful for at least two days after the drug injection. Ataxia was present at 50 mg/kg of mescaline, but not at 25 mg/kg; however, at the latter dose level, the ability to grip was impaired. Further analysis of the results showed that either age or strain, or possibly a combination of both, affected the behavioural profile of the CAR after the administration of mescaline. Mescaline does not apparently have a consistent behavioural profile when several tests are used to assess its effects. alternative hypotheses as to its action are presented: the first suggests that there is an unknown secondary metabolite present which is responsible for the changes in behaviour. The second is that an animal learns rapidly while under the effects of the drug, and that this learning is retained. It would appear that the central nervous system and the autonomic nervous system are both affected by the drug, and that peripheral effects are present.
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