Biphasic effects of melatonin on the propagation of excitation waves in the chicken retina

The retinal spreading depression (SD) is a propagating wave in an excitable medium, the neuronal tissue of the retina. Its velocity is about 3 mm/min and it is accompanied by a variety of changes in the tissue, including elec trical and optical events. The pronounced intrinsic optical signal (IOS) of the retinal SD makes it an extremely versatile tool for the investigation of the action of drugs on neuronal tissue and more specific on propagating excitation waves in neuronal tissue. Furthermore, in the last decade increa sing evidence has been collected, which shows that SD waves are the basic m echanism of the aura in classical migraine. We have investigated the influe nce of melatonin on the propagation of retinal SD waves as it has been post ulated to have protective effects on neuronal tissue. The results demonstra te that melatonin indeed slows down the retinal SD, however, only in a defi ned concentration range. Additionally, it changes the IOS of the wave. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.