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 hyper-synchronous activity observed during absence seizures. Here we investigate the correlation between the expression of T-channel coding genes (α1G, -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 α1G and α1I, while the reticular thalamic nucleus expressed α1H and α1I. 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 LTS size and the minimum LTS generating slope, while T-type Ca2+ current voltage dependency correlated with the LTS onset potential.