Opioid peptides in cerebrospinal fluid-methods for analysis and their significance in the clinical perspective

The discovery of the endogenous opioid peptide systems and their subsequent identification in human cerebrospinal fluid near 30 years ago triggered an intensive research to evaluate the function of these compounds in the clinical perspective. However, for this purpose it was necessary to develop reliable techniques with high sensitivity and reproducibility. Furthermore, it was necessary to assess the chemical nature of the opioid activity present in CSF. Therefore, research on opioid peptides in CSF have to a considerable extent been directed to attempts to characterize the peptide activity present in this fluid in order to identify suitable markers of activity in any particular opioid peptide system. In the clinic these markers have been used in attempts to correlate alterations in peptide levels to various neurological diseases. This article reviews the past and ongoing research on opioid peptide systems in CSF from human with particular emphasis on their relevance in the clinical perspective.