[Endorphins 1989: neuroendocrine aspects]

Endorphins represent a family of brain peptides having an opioid core structure responsible for their morphinomimetic activity. We present an overview of the biology of endorphins including their origin, neuroanatomical distribution, regulatory mechanisms and interaction with opioid receptors taking neuronal cellular function in situ as our focal point of interest. Differential biochemical processing and regulatory mechanisms both at the pre- and post-translational level in the various brain areas contribute to the biochemical and functional diversity of peptides generated from common precursors in keeping with the selective needs and functions of neuronal circuits. Physiological significance requires interaction of the various endogenous ligands thus generated with appropriate receptors, sometimes located well beyond the distance of a synaptic cleft as demonstrated by the diverging ligand/receptors neurochemical topographical maps. Physiological analysis reveals a multitude of potential interactions between peptides and classical neurotransmitters in part as a result of their common subcellular location within individual synaptic vesicles but also in relation to qualitatively different post-synaptic effects and metabolism, enhancing the complexity of their potential role in neuronal function. Endorphins may contribute to major neuroendocrine systems such as analgesia, endocrine and autonomic function, mental function and behavior. Their implication in various neuropsychiatric and endocrine clinical disorders will be briefly reviewed.