Does Nitrous Oxide Induce Release of Brain Opioid Peptides?

Abstract
Increased concentrations of immunoreactive Met-enkephalin but not Leu-enkephalin were measured in fractions to CSF perfusate collected from ventricular-cisternally perfused, urethane-anesthetized rats exposed to a mixture of 75% N2O/25% O2 for 60 min. N2O might be capable of inducing the release of Met-enkephalin in the CNS.