A factor isolated from Datura stramonium that affects learning retention in mice

A water-soluble fraction, devoid of alkaloids, was isolated from Datura stramonium (leaves and seeds). This fraction greatly impaired retention of (i) discriminated avoidance learning, (ii) two-way active avoidance learning, and (iii) a food-reinforced instrumental learning. The retention impairment induced by the Datura extract in these learning tasks was not due to an effect on spontaneous locomotor activity nor to changes in the emotional reactivity of the animals. Preliminary chemical analysis suggests that the active principle of the Datura extract may be a small peptide. It is suggested that this active principle affects some memory processes.