Suppression of Hippocampal Epileptiform Activity in Vitro After Laser Exposure

Abstract

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.

Effect of Infrared Laser Irradiation on Amino Acid Neurotransmitters in an Epileptic Animal Model Induced by Pilocarpine

“…42 It has been suggested that anticonvulsants generally act by increasing inhibitory GABAergic mechanisms, by depressing excitatory glutamate neurotransmission, by depressing voltage-dependent Ca 2ϩ -mobilizing mechanisms, or by depressing Na ϩ conductance. 43 Moreover, a significant decrease in the frequency and an alteration in the morphology of epileptiform discharges in the hippocampal slices resulted from irradiation with a 25-mW argon ion laser, 44 and our previous data showed that daily laser irradiation (90 mW at 830 nm) for 7 d induced a pronounced neurochemical inhibition in the cerebral cortices of rats (unpublished data). In light of these studies, the aim of the present study was to investigate the effect of daily laser irradiation (90 mW at 830 nm) for 7 d on the levels of amino acid neurotransmitters in the cortex and hippocampus of an animal model of temporal lobe epilepsy induced by pilocarpine.…”

“…65 an in vitro model of epileptiform hyperexcitability in hippocampal slices, and found a decrease in spontaneous and electrically evoked activity in this preparation after laser irradiation. 44 The authors suggested that laser irradiation mimics the effects of anticonvulsant drugs such as benzodiazepines, barbiturates, and baclofen in their blocking effect on GABA B receptors. Kataoka et al indicated that laser-induced neurosuppression may be mediated by photodynamic changes in cellular metabolism.…”