Effects ofPsychotria colorata alkaloids in brain opioid system

Abstract
An ethnopharmacological survey showed that home remedies prepared with flowers and fruits ofPsychotria colorata are used by Amazonian peasants as pain killers. Psychopharmacological in vivo evaluation of alkaloids obtained from leaves and flowers of this species showed a marked dose-dependent naloxone-reversible analgesic activity, therefore suggesting an opioid-like pharmacological profile. This paper reports an inhibitory effect ofP. colorata flower alkaloids on [3H]naloxone binding in rat striata as well as a decrease in adenylate cyclase basal activity. The alkaloids did not affect [3H] GMP-PNP binding. These findings provide a neurochemical basis for the opioid-like activity previously detected in vivo and point toPsychotria alkaloids as a potential source of new bioactive opiate derivatives.