Effects of PAF-acether on electrophysiological response of isolated retina.

Results of experiments performed on rat isolated retina indicate that platelet-activating factor (PAF) is able to inhibit the functional response of the retina electroretinogram (ERG) recorded in response to a brief light flash. In the presence of PAF, the ERG b-wave amplitude decreases according to a dose-dependent (2.10(-11) M; 2.10(-9) M; 2.10(-7) M) process. This effect is partially inhibited by the simultaneous administration of a Ginkgo biloba extract (GBE, 10 mg/l) or Ginkgolide B (BN 52021, 2.10(-5)M). The authors interpret these results with reference to the main mechanism of the membrane signal triggered by PAF, namely the activation of phosphatidylinositol cycle with the formation of inositol-triphosphate, the inhibition of the light-induced response of the retina by administration of inositol-triphosphate, and the antagonistic effect of GBE and BN 52021 on specific PAF-receptors demonstrated on other models. Thus specific PAF-receptors may exist at the level of the retina, which suggests that they are also present in the brain.