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SUMMARYPurpose: The role of the superior colliculus (SC) in seizure expression is controversial and appears to be dependent upon the epilepsy model. This study shows the effect of disconnection between SC deep layers and adjacent tissues in the expression of acute and kindling seizures. Methods: Subcollicular transections, ablation of SC superficial and deep layers, and ablation of only the cerebral cortex were evaluated in the Wistar audiogenic rat (WAR) strain during acute and kindled audiogenic seizures. The audiogenic seizure kindling protocol started 4 days after surgeries, with two acoustic stimuli per day for 10 days. Acute audiogenic seizures were evaluated by a categorized seizure severity midbrain index (cSI) and kindled seizures by a severity limbic index (LI). Results: All subcollicular transections reaching the deep layers of the SC abolished audiogenic seizures or significantly decreased cSI. In the unlesioned kindled group, a reciprocal relationship between limbic and brainstem pattern of seizures was seen. The increased number of stimuli provoked an audiogenic kindling phenomenon. Ablation of the entire SC (ablation group) or of the cerebral cortex only (ctx-operated group) hampered the acquisition of limbic behaviors. There was no difference in cSI and LI between the ctx-operated and ablation groups, but there was a difference between ctx-operated and the unlesioned kindled group. There was also no difference in cSI between SC deep layer transection and ablation groups. Results of histologic analyses were similar for acute and kindled audiogenic seizure groups. Conclusions: SC deep layers are involved in the expression of acute and kindled audiogenic seizure, and the cerebral cortex is essential for audiogenic kindling development.

We present evidence that chronic disturbances in sympathetic tone in WAR cause increases the risk to life-threatening arrhythmias. Our results support a relationship between seizures, cardiac dysfunction and cardiac arrhythmias, which may contribute to the occurrence of SUDEP.

To study the relationship between genetics and epilepsy, Wistar rats susceptible to audiogenic seizure were selected from the main breeding stock of the Ribeirão Preto School of Medicine at the University of São Paulo, Brazil, and inbred. The criteria for selection were the highest seizure severity index (SI) and shortest latencies of the first running fit (LI). Because behavioral response to sound stimulation (120 dB) at 70 to 78 days of age was very stable, SI and LI were evaluated within this age range. Analysis of 9450 observations in 1575 animals from the 3rd to 17th generations demonstrated significant effects of generation, parity, and litter on SI and of generation and litter on LI. The SI and LI averages were, respectively, 37.13 and 22.82 s in the 3rd generation and 83.06 and 7.84 in the 17th generation. Heritabilities of both characters were estimated, by maximum likelihood, as 0.37 +/- 0.066 and 0.44 +/- 0.059, respectively. Because a significant regression related individual breeding values for both SI and LI to generation number, we concluded that genetic selection has a positive impact on the traits analyzed. Therefore, the Wistar audiogenic rat (WAR) strain appears, as per the 17th to 20th generations of genetic selection to be an audiogenic rat strain suitable for epilepsy studies.

Dipyrone, a non-steroidal anti-inflammatory agent, was anticonvulsant in three experimental epilepsy models. At a dose of 300 mg/kg i.p., dipyrone blocked the maximal hind limb extension in the electroshock model in Wistar rats, the tonic-clonic component of acute sound-induced seizures and the limbic component of audiogenic kindling in genetically susceptible Wistar-derived rats, all in 100% of the animals. In the electroshock model higher doses (400 and 500 mg/kg) were also effective but lower doses (100 and 200 mg/kg) were not. In this model dipyrone had no effect on the recovery of the righting reflex and intensified the postictal antinociception in a dose-dependent manner. Other non-steroidal anti-inflammatory agents such as indomethacin, diclofenac and aspirin had no anticonvulsant effect in the electroshock-induced seizures.

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