Abstracts

In spite of anecdotal reports describing an association between chronic epilepsy and interictal aggressiveness (Geschwind, 1983), and of surveys suggesting that such an association is common in temporal lobe epilepsy (Bear and Fedio personality inventory), this concept has not been generally accepted by epileptologists. In the course of studies of the long-term consequences of untreated 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 in male Wistar rat pups at age 28 days. Chronic spontaneous seizures developed in 90% of animals. We tested rats for territorial aggression under the resident-intruder paradigm: an [ldquo]intruder[rdquo] rat is introduced into the cage of a [ldquo]resident[rdquo] rat for 15 min session. Each experimental animal was exposed to three different controls and three different experimentals as resident, and to three separate animals of each group. We measured the average number of episodes of dominant mount (ventral/dorsal contact and immobilization of opponent), pinning (ventral/ventral contact and immobilization of opponent), and agonistic behavior: attacks (lunging onto opponent), boxing (upright stance, facing opponent, pushing opponent with forepaws) and biting (direct dental contact of one rat with another). The experimentals, when observed together, showed less dominant behavior (0.8[plusmn]0.4 vs. 6.3[plusmn]2.8 mounts), more agonistic behavior (8.5[plusmn]3.3 vs. 0.5[plusmn] 0.2 boxing episodes) than controls together. The experimentals exposed to controls, expressed more dominant behavior both as a residents and as intruders (14[plusmn]4.1 vs. 2.1[plusmn]1.7, 16.7[plusmn]3.0 vs. 2.3[plusmn]1.2 mounts, respectively), and showed more frequent agonistic behavior: boxing (4.7[plusmn]1.9 vs. 0.6[plusmn]0.2, 5.5[plusmn]1.2 vs. 0.7[plusmn]0.3, respectively) and biting (7.3[plusmn]3.1 vs. 0 or 5.8[plusmn]3.0 vs. 0) than controls. The experimental rats showed more dominant behavior toward controls than toward other experimentals, in mounts (15.5[plusmn]3.1 vs. 0.6[plusmn]0.4), attacks (5.4[plusmn]2.0 vs. 1.6[plusmn]0.5) and bites (6.5[plusmn]3.5 vs. 0). Controls that faced experimentals, expressed less dominant behavior (2.2[plusmn]1.5 vs. 6.3[plusmn]2.0 mounts) and showed tendency toward increased agonistic behavior (2.0[plusmn]0.3 vs. 0 attacks) compared to facing other controls. The untreated lithium/pilocarpine SE induced a large increase in aggressive behavior, which involved all aspects of aggression in the intruder paradigm, when tested 3 months after SE. The experimentals 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 to controls when tested against each other. (Supported by VHA Research Service and by Grant RO1 NS 13515 from NINDS.)