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Impressum
Effects of sildenafil on retinal function in superfused vertebrate retina
1Lüke M., 1Lüke C., 1Walter P., 1Kirchhof B., 2Sickel W.
1Zentrum für Augenheilkunde, 2Institut für Neurophysiologie der Universität Köln
Objective: Dose-dependent clinical effects of visual disturbance
in some patients taking sildenafil (Viagra® ) have been reported.
In connection with this an inhibition of the phototransduction cascade
by interaction of sildenafil with the phoshodiesterase (PDE 6) of the
photoreceptor has recently been discussed. In the present study we investigated
the effects of sildenafil on bovine retinal function.
Methods: Bovine retina preparations were perfused with an oxygen
preequilibrated standard solution. The electroretinogram (ERG) was recorded
using AgAgCl electrodes. After recording of stable ERG amplitudes sildenafil
was added to the solution for 45 minutes. Thereupon the preparation was
reperfused with standard solution for 150 minutes. The percentage of a-
and b-wave reduction after exposition was calculated.
Results: Toxic effects of sildenafil were found for the following
concentrations:
| Sildenafil concentration | [µMol/l] | 0,1 | 0,33 | 1 |
| a-wave reduction | [%] | 13,7 | 20,4 | 34,3 |
| b-wave reduction | [%] | 16,4 | 40,7 | 64,8 |
The effects after application of sildenafil were not reversible within
the recovery time.
Conclusions: The ERG reflecting first and higher order neuron activity
of the retina showed toxic effects of sildenafil at therapeutic plasma
concentrations. As the observed effects on the b-wave distinctly exceeded
those on the a-wave the present study suggests that besides impairment
of photoreceptor function sildenafil also exerts direct effects on the
postsynaptic neuronal network of the retina.