Spreading depression in the corticostriatal system of the rat brain during a seizure process induced by the daily administration of pentylenetetrazole

: Spreading depression (SD) in the cortex and the caudate nucleus induced by 40 mg/kg i.p. pentylenetetrazole (PTZ) injection was studied in awake rats with implanted carbon electrodes. It was shown that spontaneous bilateral occurrence of cortical SD was the most probable and had an effective inhibitory influence on seizures after the first PTZ application. Penetration of cortical SD waves into the caudate nucleus and their return to the cortex substantially prolonged the anticonvulsive effects of SD. In the course of daily repeated PTZ injections the cortico-caudate SD propagation reduced progressively being accompanied by a decrease of efficiency of its inhibitory effect and interictal spike activity intensification. Similar restriction of SD propagation was observed without any seizure manifestations under the conditions of daily cortical electrical stimulation (without systemic drug treatment). So, reducing the cortico-caudate SD incidence during PTZ kindling is rather the cause of seizure facilitation than its consequence.