Abstracts

RATIONALE: This study investigates if hippocampal cells in kindled rats take up and metabolize 5-Aminoluvelinic Acid (5-ALA) more readily than hippocampal cells in non-kindled rats. 5-ALA is a component of the heme synthesis pathway and is a FDA approved drug approved for use in photodynamic therapy for certain tumors. It is converted in the mitochondria to protoporphyrin IX (PpIX), a fluorescent and photosensitizing agent. We speculate that 5-ALA is selectively taken up by cells involved in seizure generation, in vivo, and converted to PpIX, based on similarities to uptake determinants for tumors: pH, metabolism and blood brain barrier changes. Currently, electroencephalogram (EEG) is used to localize seizure initiation sites in epileptic brains. A fluorescent labeling technique would provide clinicians with another and perhaps more specific method of defining the area of seizure generation.
METHODS: We compared PpIX fluorescence in three groups of Sprague-Dawley rats: A.) fully kindled rats with elicited seizures on the day of 5-ALA infusion, B.)fully kindled rats without elicited seizures on the day of 5-ALA infusion, and C.) implanted controls. Brains were flash frozen in isopentane at -40[degree]C and sliced into 20[mu]m sections. The slices were excited at 405nm and the red wavelength emissions were captured with a SPOT digital camera. Images were analyzed after being converted to gray scale using Image-Pro software. Relative fluorescence was quantified as mean optical density of the gray scale images.
RESULTS: Preliminary data with a small number of animals suggest that fully kindled rats with elicited seizures show greater 5-ALA uptake in hippocampal cells compared with both fully kindled rats without elicited seizures and the implanted controls. Our initial results also suggest that kindled rats without elicited seizures show more fluorescence than implanted controls.
CONCLUSIONS: Preliminary evidence indicates that cells involved in seizure generation take up more 5-ALA compared to non-seizure controls. Kindling itself may also enhance 5-ALA uptake since a kindled animal without seizures showed more uptake than non-kindled controls. These initial results provide a first step towards using 5-ALA in visualization of epileptic foci and applying photodynamic therapy to epilepsy.
[Supported by: C.U.R.E and Bronte Foundation]