Suppression of Hippocampal Epileptiform Activity in Vitro after Laser Exposure

A University of California author or department has made this article openly available. Thanks to the Academic Senate's Open Access Policy, a great many UC-authored scholarly publications will now be freely available on this site. Let us know how this access is important for you. We want to hear your story! Extracellular field potentials were recorded in the stratum pyramidale of CA3 in hippocampal slices prepared from male Sprague-Dawley rats. Electrical stimuli were delivered to s. radiatum of CA3. After stable responses were established, stimulus trains were delivered every 5 mm until stable triggered and spontaneous population bursts were elicited. The slices were then irradiated with a low power (25 mW) argon laser. No changes in the morphology or number of epileptiform bursts were found while the laser was on. However, when the laser was turned off, there was a highly significant reduction in frequency and morphology of bursts. These results indicate that exposure to light alters epileptiform activity within the hippocampus in vitro, and provides evidence indicating that the central nervous system is photosensitive.