Investigation of endogenous opioid reactivity with fentanyl challenge in major depression and self-injurious behavior

Some observations support the notion that regulation of the endogenous opiate system is deficient in major depression and sleep deprivation might exert its antidepressant properties via opioid mediation. In another psychiatric condition, namely stereotypic movement disorder, the clinical use of opiate antagonists have shown to diminish self-injurious behavior supporting involvement of opiate mechanisms in this pathological condition. The overall aim of presented studies was to elucidate the role of the endogenous opiate system in the pathomechanism of major depression, self-injurious behavior and in the antidepressant action of partial sleep deprivation. The main method applied was the use of the selective mu-receptor agonist fentanyl, as a challenging agent for testing endogenous opiate sensitivity by monitoring neuroendocrine responses to the drug, particularly measuring fentanyl-induced plasma levels of prolactin. The author had studies focusing on dose-response relationships in healthy volunteers and diurnal changes of opiate sensitivity. His subsequent studies utilized these results and addressed opioid mechanism in depression, self-injurious behavior and after partial sleep deprivation. Based on data obtained by fentanyl challenge tests, it seems possible that endogenous opiates play some role in the conditions investigated. The author of these short publications wishes to avoid oversimplification and is careful about drawing conclusions for treatment strategies from these findings. The role of the endogenous opiate system in psychiatric illnesses and pathological behaviors is not simple and can be best explained in interaction with other neurotransmitter and signal processing mechanisms.