Hyperbaric pressure does not affect the analgesia produced by nitrous oxide in the mouse.

Hydrostatic pressure antagonizes some, but not all, of the phenomena associated with general anaesthesia. For example, while unconsciousness produced by general anaesthesia in a wide variety of species is reversed by compression, anaesthetic-induced inhibition of synaptic transmission is potentiated by application of pressure. To date, the effect of pressure on analgesia has not been evaluated. In this study, hyperbaric pressure of 75 ata did not antagonize analgesia which had been produced by exposure of mice to 1.2 ata of nitrous oxide. However, the same hyperbaric pressure restored righting in animals which had been anesthetized with 1.5 ata of nitrous oxide. These data add to the suggestion that the multiple effects of general anaesthetics may be mediated at different loci.