Decrease of beta-endorphin in the brain of rats following nitrous oxide withdrawal

beta-Endorphin levels in the whole rat brain were not changed during acute (25 min) or chronic (48 h) exposure of rats to N2O. However, a significant decrease of beta-endorphin was found in the whole brain, brain stem and subcortex during the withdrawal from chronic exposure to N2O. It has been suggested that decrease of beta-endorphin levels during N2O withdrawal could be ascribed to unspecific stress accompanying drug withdrawal. Decrease of central beta-endorphin during N2O withdrawal might have a significant modulatory effect on transmitter balance, neuronal excitability and corresponding withdrawal behaviour. Furthermore, the decrease of beta-endorphin levels in the whole brain during N2O withdrawal might contribute to the postanaesthesia N2O-excitatory syndrome in humans. This might explain the known therapeutic effect of the opioid drug, meperidine on the excitatory N2O withdrawal phenomena during recovery from N2O anaesthesia in man.