The influence of phosphodiesterase inhibitors on ERG and optic nerve response of the cat.

Reversible changes in electroretinograms (ERG) and optic nerve responses (ONR), induced by various concentrations of four different types of phosphodiesterase (PDE)-inhibitors, were recorded from arterially perfused, isolated cat eyes. In the dark-adapted eye, the implicit time of the PIII-component of the ERG, isolated by temporary hypoxia, showed a dose-dependent increase after the injection of PDE-inhibitors into the ophthalmociliary artery. The PIII-amplitude increased in response to small doses of PDE-inhibitors, whereas higher doses led to an amplitude decrease. Rod b-wave amplitude and implicit time showed similar alterations. An amplitude increase could not be observed in the rod ONR. In the light-adapted eye, 440 nm and 555 nm cones were functionally separated by means of chromatic adaptation. Their ERG and ONR implicit times were prolonged under PDE-inhibition. The amplitude behaviour of both types of cones showed a different concentration dependency. Certain concentrations of PDE-inhibitors depressed the short-wavelength sensitive cone, while, at the same time, sensitizing the long-wavelength sensitive cone. The amplitude increase of the L-cone b-wave was accompanied by a response increase of tonic ganglion cells in the ONR.