C. Montigny, G. Aghajanian
Dec 1, 1977
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Neuropharmacology
Abstract
Abstract The effects of iontophoretic application of 5-methoxytryptamine (5-MeOT) and 5-methoxy-dimethyltryptamine (5-MeODMT) were studied on serotonin (5-HT)-containing neurones of the mid-brain raphe nuclei (presynaptic area) and on neurones of two representative postsynaptic areas, the lateral geniculate body (ventral nucleus) and the amygdala (median, cortical and basolateral nuclei) which both receive a dense 5-HT input from the midbrain raphe. The effects of 5-MeOT and 5-MeODMT were compared to that of lysergic acid diethylamide (LSD) and 5-HT applied to the same neurones. All four substances depressed neuronal firing in the three areas. Lysergic acid diethylamide, 5-MeODMT and 5-MeOT were found to exert a much more powerful effect on presynaptic (5-HT) neurones whereas 5-HT was slightly more active in depressing postsynaptic (amygdala and geniculate) neurones. The ratios of the pre- and postsynaptic efficacies were calculated to be 5.6, 4.3, 1.8 and 0.7 for LSD, 5-MeODMT, 5-MeOT and 5-HT respectively. Since a correlation between the hallucinogenic efficacy of indoleamines and their preferential presynaptic effect has been described, these results are in agreement with the reported hallucinogenic potency of 5-MeODMT and suggest that 5-MeOT could also have psychotomimetic properties.