Anesthesia does not increase opioid peptides in cerebrospinal fluid of humans.

One theory of narcosis postulates that inhaled anesthetics produce general anesthesia by causing the release of endogenous opioid peptides. In the present study, however, the concentration of immunoreactive beta-endorphin-like material (eight patients) or leu-enkephalin (four patients) did not increase in cerebrospinal fluid of patients 5 min after induction of anesthesia with thiopental, 2-5 mg/kg and N2O 70%; after an additional 10 min, during which halothane was added; at 5, 15, and 60 min after surgical incision; or after 30 min in the recovery room. Therefore, any contribution of the endorphin system to the production of general anesthesia does not appear to require the release of beta-endorphin.