Abstract
Feline generalized penicillin-induced epilepsy is a reliable experimental model of epileptic photosensitivity. Binocular photic stimulation at 4-8 flashes/s consistently triggers generalized, bilaterally synchronous spike-and-wave discharges in cats submitted to long-term i.m. penicillin administration at low dosage (50,000-150,000 IU/kg). The photically induced epileptic activity is 1st and mainly recorded from the cerebral cortex as compared with the lateral geniculate (GL) body, supporting a cortical onset of epileptic photosensitivity. At this low penicillin dosage, only minimal spontaneous spike-and-wave activity is recorded. Bilateral GL stimulation is more effective than binocular photic stimulation in triggering spike-and-wave discharges, whereas unilateral GL stimulation is grossly ineffective. A role of bilateral specific visual thalamocortical volleys in the genesis of epileptic photosensitivity is implied. Of 12 randomly selected cats receiving long-term penicillin 5 exhibited spontaneous epileptic photosensitivity. An underlying genetic predisposition of the feline species to this condition is suggested.