Study on mammal (rat) of the neuro-muscular synapse function under hyperbaric conditions (11 ata): effects of the...

Under hyperbaric conditions (11 ata) obtained with normoxic O2-N2 mixtures spontaneous EMG activity disappears, as do reactions to noise, but this phenomenon is reversible after the substitution of Helium for Nitrogen in the mixture. Analysis of EMG responses to sciatic nerve excitation has revealed no difference between the EMG tracings recorded under normobaric pressure and those obtained under hyperbaric conditions (O2-N2 or O2-He, 11 ata), and hyperbaric conditions do not seem to interfere with neuro-muscular synaptic transmission. Furthermore, the effect of Pavulon (an antidepolarising, acetyl-cholino-competitive curare-mimetic drug) is similar under normal and hyperbaric conditions: hyperbaria change neither the onset of neuro-muscular blockage nor its intensity or duration. The absence of a specific effect on synapse function of a change in the diluting gas from nitrogen to helium suggests that there was no change in post-synaptic receptor function. This result is not in accordance with the hypothesis that inert gas pressures of less than 10 ata modify molecular structures particularly at the neuro-muscular synapse level.