Role of the superior colliculus in the expression of acute and kindled audiogenic seizures in Wistar audiogenic rats.
OBJECTIVE
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.
Doretto
Maria C
MC
Physiology Department, Ribeirão Preto School of Medicine, University of São Paulo, São Paulo, Brazil.
Cortes-de-Oliveira
José A
JA
Rossetti
Franco
F
Garcia-Cairasco
Norberto
N
D000161:Acoustic Stimulation; D000208:Acute Disease; D000818:Animals; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology; D002541:Cerebral Decortication / Q000379:methods; D004195:Disease Models, Animal; D004569:Electroencephalography; D020195:Epilepsy, Reflex / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D007696:Kindling, Neurologic / Q000502:physiology*; D008032:Limbic System / Q000503:physiopathology; D008297:Male; D008636:Mesencephalon / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012720:Severity of Illness Index; D013477:Superior Colliculi / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery