Technical note: Preliminary results in development of a novel intracisternal penicillin seizure model in the rat

In order to develop an intracisternal penicillin rat model of epilepsy, eleven anesthetized male Wistar rats were studied. 5 underwent intracisternal injection of penicillin (doses 150,000-300,000 units) in the prone position, and another 5 underwent intraperitoneal penicillin injection; one died following intracisternal injection, prior to further study. Time between penicillin injection and seizure induction (determined by electroencephalography) was recorded. Each animal had a tracheostomy, and was mechanically ventilated and carefully monitored for adverse effects. Seizures were noted in an average of 13:42 minutes following penicillin injection (range 4:30-23:20) for the intracisternally (IC) injected group. Both episodic and continuous seizure activity was seen, and a dose-dependent effect was seen (quicker-onset, more continuous seizures with higher doses, in the IC group). Onset was significantly faster in the IC than for the intraperitoneally injected group (all >1 hour for the latter group in our study). 96 total separate seizure episodes were seen, ranging from 3 to 540 seconds. Epileptic activity could be seen in all IC-injected rats lasting over 1 hour into the study. The intracisternal penicillin injection rat model appears to provide a quick-onset, reliable method of inducing seizure activity in the rat model while leaving the cranial vault intact.