Helium pressure alteration of function in squid giant synapse

The squid giant synapse, which permits intracellular electrical measurements in a single, excitatory synapse, was exposed to helium pressures up to 204 atm. By stimulating presynaptically and recording postsynaptically with an intracellular electrode it was found that pressure alters, but does not prevent, synaptic transmission of action potentials. Synaptically transmitted action potentials are prolonged in the same way as in the directly stimulated axon. However, slowing of the excitatory postsynaptic potential and marked increases in synaptic fatigue were observed at pressures as low as 35 atm. These changes may contribute to high pressure nervous effects by interfering with information transfer within the nervous system.