Abstracts

To define the posttraumatic dynamic changes of the benzodiazepine receptor antagonist [¹¹C]flumazenil binding in the rat model of focal chronic epilepsy.
Twenty-four male Sprague-Dawley rats, six animals in each group were used. Surgery according to the model of focal chronic epilepsy as initially described by Willmore was performed. Twelve of the rats were injected with iron chloride and twelve with artificial CSF. The rats were decapitated after 1 day, 5 days, 3 months and 6 months after surgery and the brains were rapidly frozen.
Frozen sections of 20 micrometer were cut with a cryostat microtome, mounted on gelatin-coated glass slides, dried in room temperature and stored in -20[deg]C freezer until used.
The sections were preincubated in Tris-HCl, thereafter incubated in 10nM [¹¹C]flumazenil for 50 minutes. Non specific binding was determined in adjacent sections incubated in the presence of 1 [mu]M Ro15-1788. After incubation sections were washed twice for one minute in the incubation buffer and dried under a steam of warm air.
For quantification, an individual calibration standard was prepared for each set of brain sections and exposed to the same imaging plate.
For radiation detection, Storage Phosphor (SP) plates (Molecular Dynamics) were used. The glass slides were exposed for 40 minutes where after the plates were scanned with a laser beam in a phosphor imager. Individual region of interests (ROIs) were outlined in each section to measure the signal in the ipsi- and contra lateral areas of the affected cortex adjacent hippocampal structures.
Statistics were calculated with students t-test.
The cortical binding of [¹¹C]flumazenil was significantly decreased in the ferrous chloride injected cortex as compared to the contra lateral side at all four time points. The binding was also significantly lower in the ferrous chloride injected cortex as compared to the control rats at one day, five days and three monts. However, at six months no the difference did not reach statistical significance. Furthermore, in the injected focus, the absolute binding was decreased between day one, day five and three months. with a small increase of binding between three and six months.
Decreases in cortical [¹¹C]flumazenil binding in the rat model of focal chronic epilepsy is prominent and significantly changed as compared to the contra lateral cortex at one day after the injection of ferrous chloride. This difference is continuos and does not decrease after five days, three or six months.