EFFECTS OF NITRIC-OXIDE ON THE RETINAL SPREADING DEPRESSION

The retinal spreading depression has been used as a tool to investigat e the action of nitric oxide (NO) as a diffusible neurotransmitter whi ch in many cases acts by raising the cGMP level in target cells. The r ole of NO as a vasodilating agens has been well-established and it has been suggested that the vasodilatation concurrent with cortical SD ma y be mediated by NO. In this study, we present pure neuronal effects o f NO on SD as the chicken retina is void of bloodvessels. We show that NO directly decreases the velocity of retinal SD waves in a concentra tion-and time-dependent manner. This effect can be partially mimicked by application of membrane-permeable cGMP derivatives. Furthermore, a NO-mediated speed up of the recovery of the intrinsic optical signal a fter the wave-front is shown.