Opiate receptors and endogenous opiates: panorama of opiate research.

1. In the last ten years basic research on the mechanism of action of opiates has led to the clearcut demonstration of the existence of opiate receptors--possibly several slightly different kinds--in the nervous system. 2. A number of endogenous ligands also called endorphins or enkephalins for these receptors have been discovered that proved to be peptides with opiate-like pharmacological activity and were shown to be localized in strategic neuronal pathways in the brain, spinal cord and pituitary gland. 3. Clinical researchers are beginning to explore the possible role of these opiate-like peptides in a variety of clinical situations such as: pain and analgesia, tolerance and dependence, reinforcement mechanisms, memory processes and learning, and mental illness such as schizophrenia. 4. The discovery of biologically active opioid and other peptides coexisting with more traditional neurotransmitters in the same neurons may lead to a reevaluation of our fundamental notions of how the brain operates. This is viewed as a major advancement not only to our understanding of the theoretical basis of drug actions but also as a first step towards the development of new, practically useful methods for treating the clinical problems associated with drug abuse.