Attenuation of amnesia in rats by systemically administered enkephalins.

The pentapeptides methionine-enkephalin and leucine-enkephalin are both able to reduce experimentally induced amnesia in rats. In contrast to the possible analgesic activity of these peptides, the anti-amnesic effect is seen after systemic administration of dosages of 30 micrograms or lower. The nature of the anti-amnesic effect is different for the two peptides.