Different behavioral and electrographic effects of acoustic stimulation and dibutyryl cyclic AMP injection into the inferior colliculus in normal and in genetically epilepsy-prone rats

The behavioral and electrographic effects of acoustic stimulation (100 dB) and injection of dibutyryl cyclic AMP (cAMP, 10 nmol) into the inferior colliculus were studied in normal and genetically epilepsy-prone (GEPR-9) rats. Acoustic stimulations induced behavioral seizures only in GEPR-9 rats; the seizures were associated with electrographic epileptiform discharges recorded from the inferior colliculus. Injections of dibutyryl cAMP into the inferior colliculus caused wild running episodes resembling the initial phase of audiogenic seizures in both groups. However, in GEPR-9 rats these episodes progressed to significantly more severe seizures than in normal rats and the convulsions culminated into status epilepticus. During drug-induced seizures, epileptiform activity was present in the inferior colliculus in both groups. The seizure generalization latency was markedly shorter in GEPR-9 rats than in normals. Furthermore, in GEPR-9 rats, the seizure generalization latency was in the same range with either acoustic stimulation-induced or dibutyryl cAMP-induced seizures. The data suggest that the increased susceptibility of genetically epilepsy-prone rats to acoustic stimuli may be related to a malfunction of the cyclic AMP system within the inferior colliculus.