A comparison of the effects of morphine sulphate and nitrous oxide analgesia on chronic pain states in man.

The effect of nitrous oxide and morphine sulphate on chronic pain states in man are compared. The similarity of effect indicate that nitrous oxide acts on the morphine receptor. In all cases where analgesia was produced naloxone reversal occurred. These results provide additional evidence for a dual system hypothesis of pain perception and that nitrous oxide analgesia is mediated by the endogenous opiate system. In the light of these findings, the possibility of using nitrous oxide to replace morphine sulphate as a screening test for deep brain stimulation analgesia is discussed.