AN ELECTROGRAPHIC STUDY OF PSILOCIN AND 4-METHYL--METHYL TRYPTAMINE (MP-809)

¹ Thudichum Psychiatric Research Laboratory, Galesburg State Research Hospital, Galesburg, Illinois

In this study 59 rabbits were used for an EEG analysis of five compounds: O-phosphoryl-4-hydroxy-N-dimethyl tryptamine (psilocybin), 4-hydroxy-N-dimethyl tryptamine (psilocin), 4 - methyl - - methyl tryptamine (MP-809), 4-hydroxy--methyl tryptamine (MP-l4) and 1-methyl psilocybin. Four different preparations were employed, two involving transection of the brain and one of the cervical cord. In experiments on the intact brain groups of 6 rabbits were used and each of the five compounds was tested. The precollicular, prepontine preparation was employed in ten rabbits to localize sites of action of MP-809 and psilocin. In other experiments involving the postcollicular, postpontine transection 15 animals were studied for additional information on the same two drugs. In addition, 4 animals having a transection at the level of the first cervical vertebra were used in a further study of psilocin.

In rabbits with intact brain all five drugs produced EEG alert patterns. When MP-809 was administered to animals transected in a prepontine, precollicular plane only a slight lowering of amplitude was seen in the EEG pattern. But when one-third the dose of eserine needed to evoke sustained activation in an animal so transected was administered to animals pretreated with MP-809 a fully alert pattern was obtained indicating a site of minor action rostral to the midbrain and probably cholinergic in nature. When, however, MP-809 was administered to animals transected in a postcollicular, postpontine plane the EEG pattern duplicated, with minor variations, the EEG arousal seen in intact animals. Thus a potent site of action for MP-809 was found in the midbrain, a region possessing a strong adrenergic component. Psilocin failed to evoke alert patterns in animals transected either rostral or caudal to the midbrain, thus excluding the midbrain and structures more rostrally situated as possible sites of action. On the other hand, animals injected with psilocin and subsequently transected at the level of the first cervical vertebra continued to display EEG alerting thus indicating a site of action below the midbrain but excluding the spinal cord. It is not likely that small changes in brain serotonin or in systemic blood pressure could account for the alterations in EEG produced by these two drugs.

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				Y. Takeo and H. E. Himwich Mescaline, 3,4-Dimethoxyphenylethylamine, and Adrenaline: Sites of Electroencephalographic Arousal Science, December 3, 1965; 150(3701): 1309 - 1310. [Abstract] [PDF]