Nitrous oxide analgesia and the endogenous opioid system.
D000698:Analgesia; D000768:Anesthesia, General; D004723:Endorphins / Q000378:metabolism*; D006801:Humans; D009609:Nitrous Oxide / Q000008:administration & dosage*
D004723:Endorphins; D009609:Nitrous Oxide