Action of opiate peptides on the release of brain acetylcholine

The effect of two naturally occurring opiate peptides, methionine-enkephalin (MET-ENK) and leucine-enkephalin (LEU-ENK) on the in vivo release of acetylcholine (ACh) from the cerebral cortex was investigated in the rat. It is concluded that MET-ENK and LEU-ENK influence the cortical release of ACh by a selective action on central opiate receptors, and suggested that one of their physiological roles may be modulated of activity in the central cholinergic pathways.