Morphologic and neurochemical alterations in the superior colliculus of the genetically epilepsy-prone hamster (GPG/Vall)

Abstract

The GPG/Vall hamster is an animal model that exhibits seizures in response to sound stimulation. Since the superior colliculus (SC) is implicated in the neuronal network of audiogenic seizures (AGS) in other forms of AGS, this study evaluated seizure-related anatomical or neurochemical abnormalities in the SC of the GPG/Vall hamster. This involved calbindin (CB) and parvalbumin (PV) immunohistochemistry, densitometric analysis and high performance liquid chromatography in the superficial and deep layers of the SC in control and epileptic animals. Compared to control animals, a reduction in SC volume and a hypertrophy of neurons located in the deep layers of the SC were observed in the epileptic hamster. Although, analysis of CB-immunohistochemistry in the superficial layers did not show differences between groups, analysis of PV-immunostaining in the deep SC revealed an increase in the mean gray level within immunostained neurons as well as a decreased immunostained neuropil in the GPG/Vall hamster as compared to control animals. These alterations were accompanied by a decrease in the levels of GABA and increased levels of taurine in the epileptic animal. These data indicate that the deep SC of the GPG/Vall hamster is structurally abnormal; suggesting its involvement in the neuronal network for AGS.