Abstracts

Rationale: Febrile seizures (FS) affect 2-5% of the pediatric population. Most FS are benign but approximately 25% have atypical features which increases the subsequent risk of developing mesial temporal lobe epilepsy (MTLE). The seizures associated with MTLE are usually intractable to treatment and are associated with significant comorbidities such as learning and memory deficits as well as anxiety and depression. Uncontrolled seizures may alter the topographical representation of motor maps (PMID: 18572991). In rodents the motor cortex is mapped by stimulating pools of pyramidal neurons in layer V of the neocortex. Previous research has demonstrated that rats having had multiple electrically induced seizures exhibit increases in the size of their motor maps. This study examined the effects of EFS in immature rodents with subtle preexisting cortical dysplasia on the size of forelimb motor maps in a model of MTLE. Methods: To reduce variability in the data only male rats were used. A cortical freeze lesion was induced on postnatal (P) day 1 (n = 5). Then pups were exposed to EFS at P10. To induce EFS pups were placed in a Plexiglas box, through which warm, dry air (45-50oC) was circulated using a standard hair dryer. The pups remained in the box until a generalized convulsion occurred, and then were immediately transferred to a cool surface where they were allowed to recover. Subsequently, between P83-115, rats underwent high resolution intra-cortical microstimulation (ICMS) under ketamine and xylazine anesthesia to produce forelimb motor maps. Controls were 1) naïve (n = 5), 2) sham lesion (n = 3), 3) sham lesion + EFS (n = 5). Results: There was a significant effect of group on map size F(3,14) = 5.519, p = 0.01. Rats that received a freeze lesion + EFS had significantly larger motor maps compared to sham lesion (p = 0.012) and naïve (p = 0.030) rats respectively. Independent samples t-tests were used to compare motor map size differences between the right (ipsilateral to sham/freeze lesion) and left (contralateral to sham/freeze lesion) hemispheres of all the groups. In each group there was no significant difference in motor map size between the two hemispheres. Conclusions: The results of this study indicate that EFS induced in rats with pre-existing lesions alters motor map expression. Further studies are needed to investigate how skilled forelimb movements are affected in this model of MTLE.