Theophylline abolishes the light peak in perfused cat eyes

Theophylline, a phosphodiesterase inhibitor, was applied to the arterially perfused cat eye in vitro. At a concentration of 850 microM, theophylline abolished the light peak of the DC-ERG and led to a 20% increase in perfusate flow to the eye. The effects were reversible. An experimentally-induced increase in flow per se by 20% resulted in a slight enhancement of the light peak. The data suggest the involvement of cyclic nucleotides in the generation of the light peak. Theophylline also caused a decrease in the standing potential of the eye, an increase in the b-wave amplitude, and a decrease in the c-wave amplitude in a dose-dependent and reversible manner.