Correlation of T-channel coding gene expression, IT, and the low threshold Ca2+ spike in the thalamus of a rat model of absence epilepsy

T-type Ca2+ Current-dependent burst firing of thalamic neurons is thought to be involved in the hypersynchronous activity observed during absence seizures. Here we investigate the correlation between the expression of T-channel coding genes ((alpha 1G, -H, -I), T-type Ca2+ current, and the T-current-dependent low threshold Ca2+ spike in three functionally distinct thalamic nuclei (lateral geniculate nucleus; centrolateral nucleus; reticular nucleus) in a rat model of absence epilepsy, the WAG/Rij rats, and a non-epileptic control strain, the ACI rats. The lateral geniculate nucleus and centrolateral nucleus were found to primarily express alpha 1G and alpha 1I, while the reticular thalamic nucleus expressed alpha 1H and alpha 1I. Expression was higher in WAG/Rij when compared to ACI. The T-type Ca2+ current properties matched the predictions derived from the expression pattern analysis. Current density was larger in all nuclei of WAG/Rij rats when compared to ACI and correlated with ITS size and the minimum LTS generating slope, while T-type Ca2+ current voltage dependency correlated with the LTS onset potential. (C) 2008 Elsevier Inc. All rights reserved.