[Electroencephalographic activity of a fish (Anguilla anguilla L.) exposed to various hyperbaric conditions (author's...

1. As a continuation of previous work where our methods were fully described (Barthelemy et al., J. Physiol., Paris, 1975, 70, 173-183), the present paper consists of research on EEG activity modifications in the eel (Anguilla anguilla L.) submitted to different hyperbaric conditions (fig. 1). 2. In contrast with mammals, the fish makes it possible to isolate the specific effects of per se pressure: those were researched to a maximum pressure of 101 ATA. Slow and sharp-pointed theta waves appear on EEG tracings of the telencephale, and especially of the tectum opticum (fig. 3), at pressures reaching or beyond 21 ATA, and then they dissappear gradually at higher pressures (101 ATA). The comparison between these effects of per se pressure on the EEG of the fish and the modifications of the EEG of mammals under hyperbaric conditions drives the authors to assume that per se pressure plays a part in the determinism of High Pressure Nervous Syndrome as described for mammals. 3. When submitted to a 21 ATA pressure (below the threshold of per se pressure effects), but when the water and his organism are satured with the N2-O2 mixture (99-1%), the fish shows no EEG modifications to be attributed to inert gas and similar to the EEG symptoms of inert gas narcosis described for mammals when exposed to the same inert gas partial pressures (fig. 5).