COMPARISON OF BENZODIAZEPINE RECEPTOR AND REGIONAL CEREBRAL BLOOD-FLOW IMAGING OF EPILEPTIFORM FOCI IN HIPPOCAMPAL-KINDLED RABBITS - A STUDY WITH IN-VIVO DOUBLE TRACER AUTORADIOGRAPHY USING I-125 IOMAZENIL AND TC-99M-HMPAO

To clarify experimentally whether benzodiazepine (Bz) receptor or regional cerebral blood flow (rCBF) imaging is more sensitive in the detection of epileptic foci, we simultaneously examined the Bz receptor and rCBF distribution changes in hippocampal kindled rabbits with in vivo double tracer autoradiography using I-125-labeled Ro 16-0154 (I-125-Iomazenil) and Tc-99m-labeled hexamethylpropylene amine oxime (Tc-99m-HMPAO). In visual and quantitative analyses, I-125-Iomazenil accumula tion in brain slices extracted after the completion of the kindling was markedly and extensively decreased in the kindled right CA1 region, and further in;the right temporal lobe, dentate gyrus, CA2, CA4, and bilateral CA3 regions, regarded as the propagated sites of seizure discharges. Tc-99m-HMPAO accumulation was much more slightly and less extensively decreased in the right CA1, frontal, temporal and dentate gyri. Further, this decrease in I-125-Iomazenil accumulation was not due to neuropathological abnormalities, which consisted only of tissue damage corresponding to electrode track in the CA1. Both the kindled and propagated sites are known to have a possibility of acquiring epileptogenesis as experimental epileptic foci. These results suggest that Bz receptor imaging is much more sensitive in the detection of epileptic foci than rCBF imaging, and therefore that Bz receptor imaging is useful in clinical epilepsy.