Water involvement in the mechanisms of retina electrical activity.

Retina is an excitable system containing approximately 90% water. As we found that deuteration selectively changes amplitudes and latencies of retina biopotentials, specifically the ON and OFF responses, we used it to probe the role of water in those processes. A study of the retina deuteration kinetics was simultaneously performed. This revealed the existence of at least two retinal water compartments. The data suggested a third compartment also, with a lower motional "degree of freedom," existing where H2O-D2O exchange becomes important only after saturation by D2O of the first two compartments. Correlation of the electrophysiological effects of D2O with the kinetic data suggests that the ON response is related to the first water compartment and the OFF response to the third. The results point to independence on the ON and OFF response mechanisms and, very probably, to their different morphological origins.