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Role of the Superior Colliculus and the Intercollicular Nucleus in the Brainstem Seizure Circuitry of the Genetically Epilepsy‐prone Rat
Author(s) -
Merrill Michelle A.,
Clough Richard W.,
Jobe Phillip C.,
Browning Ronald A.
Publication year - 2003
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1046/j.1528-1157.2003.31802.x
Subject(s) - superior colliculus , inferior colliculus , midbrain , brainstem , bicuculline , neuroscience , paramedian pontine reticular formation , epilepsy , periaqueductal gray , tonic (physiology) , reticular formation , tectum , stimulation , tegmentum , anatomy , biology , nucleus , medicine , central nervous system , receptor , gabaa receptor
Summary: Purpose: The neuronal network responsible for the convulsive behavior associated with sound‐induced seizures in genetically epilepsy‐prone rats (GEPRs) is believed to include the inferior colliculus and other brainstem structures such as the deep layers of the superior colliculus (DLSC), periaqueductal gray, and pontine reticular formation. However, previous studies also suggested that the DLSC and the nearby intercollicular nucleus (ICN) are part of a midbrain anticonvulsant zone capable of suppressing tonic convulsions when activated with bicuculline. Our aim in this study was to investigate the role of the superior colliculus (SC) and the ICN in generalized tonic–clonic seizures (GTCSs). Methods: Bilateral lesions of the SC and the ICN as well as bicuculline infusions into the ICN were used to assess the role of this dorsal midbrain region in brainstem seizures induced by sound stimulation in GEPR‐9s and GEPR‐3s. Results: Lesions of the SC markedly attenuated audiogenic seizure (AGS) severity by abolishing all behavioral components except the wild running. Lesions of the ICN significantly reduced seizure severity in GEPR‐9s, but were somewhat less effective than SC lesions. Bicuculline infusion into the deep layers of the SC and/or the ICN produced audiogenic‐like seizures in GEPR‐9s. Conclusions: These findings support the hypothesis that the SC and ICN are important components of the brainstem seizure network, but suggest they are not necessary for the wild‐running component of the seizure. The results further indicate that stimulation of the tectum facilitates GTCSs. Thus these findings suggest that the dorsal midbrain, when stimulated, is proconvulsant rather than anticonvulsant regarding brainstem seizures in GEPRs.