Alterations in t-butylbicyclophosphorothionate binding in the brains of lidocaine-kindled rats.

This autoradiographic study examines regional GABAA receptors in lidocaine-kindled rats. [35S]t-Butylbicyclophosphorothionate (TBPS), which binds in or near the chloride channel, was used to radiolabel GABAA complexes. Male Sprague-Dawley rats were injected daily with lidocaine (65mg/kg, i.p.). Seizure activity was evaluated using the Racine Scale (Racine, 1972). The animals displayed a gradual increase in the indices and by day 20 greater than 50% were in stage 4 or 5. Regression of behavior was seen in half of the experimental group and this subgroup was considered 'compensated'. Autoradiographs were analyzed using a computer-based image analysis system. Several regions within the kindled group display a decrease in TBPS binding, including the subiculum, posterior lateral thalamic nuclei, the lateral hippocampus CA1, and the lateral hippocampus CA3. Conversely, within the compensated group these regions display normal or heightened TBPS binding. The data support the theory that alterations in the GABAA receptors are involved in the kindling model of epilepsy.