Autoradio graphic study of the cerebral blood flow and neuro transmitter receptor in epleptic focus using the double tracer technique

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Cerebral blood flow (CBF) and neuro transmitters (NMDA,Acetylocholine, GABA,Benzodiazepine, 5-HT) in kainic acid induced epilepsy models were studied by multiple tracer auto radio graphy. The kainic acid (KA), 2 mug/mul, was injected into the left amygdala of Wistar rats through previously implanted cannula in awake and unrestrained condition. All rats with the KA injection developed limbic seizure as reported earlier. One month after the KAinjection, femoral artery and vein of the rats were cannulated under Halothane anesthesia. After recovery from tlhe anesthesia, the rats were injected with ^<14>C-IAP.Serial arterial blood samplings were performed and the rats were decapitated 30 seconds after the ^<14>C-IAP injection. The brain was quickly removed and frozen. Serial coronal sections were made with a cryostat. The CBF was measured by ^<14>C-IAP in vivo autoradio graphy. The adjacent slices were washed with Tris buffer to remove the ^<14>C-IAP.In vitro multiple tracer autoradio graphy on these adjacent sections was performed using ^3H-MK801, ^3H-QNB,^3H-Muscimol, ^3H-Ro15-1788, ^3H-5-HT.The receptor bindings were measured with image analyzer. The CBF was decreased in the left amygdala and all regions of the hippocampus. All the receptor bindings were decreased in the left amygdala and pyrmidal cell layr of the left hippocampus. However, the GABA,Benzodiazepine, 5-HT receptors were inversely increased in the fascia dentata of the hippocampus bilaterally. The changes of neuro transmitter receptor tend to be more restricted in the brain than that of CBF.Similar results were obtained from the clinical study of the human patients with temporal lobe epilepsy in our institution. Neuro imaging of the neuro transmitter receptor using the SPECT or PET scan seems to be very promissing for the localization of the epileptic focus.