Interictal aggression in rats with chronic seizures after an early life episode of status epilepticus

In spite of anecdotal reports describing an association between chronic epilepsy and interictal aggressiveness, and of a few studies suggesting that such an association is common in temporal lobe epilepsy, this concept has not been generally accepted by epileptologists. In the course of studies of the long-term consequences of limbic status epilepticus (SE) in juvenile rats, we noticed that experimental animals, unlike littermate controls, could not be housed together because of severe fighting. We now report a study of interictal aggression in those rats.

Long-term behavioral consequences of lithium/pilocarpine SE were studied 3 months after SE had been induced with lithium and pilocarpine in male Wistar rats at age 28 days. Chronic spontaneous seizures developed in 100% of animals. We tested rats for territorial aggression under the resident-intruder paradigm. We measured the number of episodes of dominance (mounting and pinning), and agonistic behavior (attacks, boxing, and biting).

Untreated lithium/pilocarpine SE induced a large increase in aggressive behavior, which involved all aspects of aggression in the resident-intruder paradigm when tested 3 months after SE. The experimental rats were dominant toward the controls, as residents or as intruders, and showed episodes of biting and boxing rarely displayed by controls. They also displayed increased aggressiveness compared with controls when tested against each other.

This robust model offers an opportunity to better understand the complex relationship between seizures, epilepsy, and aggression, and the role of age, SE vs. recurrent spontaneous seizures, and focal neuronal injury in the long-term behavioral effects of SE.