T-type calcium channel and Kir 4.1 potassium channel gene expression in thalamic reticular nucleus and somatosensory cortex of WAG/Rij rat strain

Abstract

WAG/Rij rat strain is inherited model of human childhood absence epilepsy. Genetic mechanisms of seizures are unknown but it was shown that reticular thalamic nucleus (RTn) and somatosensory cortex (’cortical focus’) are involved in appearing of spike-wave discharges (SWD) origin. T-type calcium channels are long suspected players in development of SWD in thalamocortical loop; Kir 4.1 is essential channel for normal physiology of cortical astrocytes involved in the glutamate uptake. We examined mRNA expression level of Kir 4.1 in somatosensory ’cortical focus’ and three T-channels alpha1-subunits in both ’cortical focus’ and RTn of WAG/Rij strain compared to control Wistar rats by means of RT-qPCR. We found CACNA1I>>CACNA1G>CACNA1H in RTn of both strains. In ’cortical focus’ tissue mRNA quantity was CACNA1I>CACNA1G>>CACNA1H for Wistar and CACNA1I=CACNA1G>>CACNA1H for WAG/Rij strain. CACNA1G mRNA is slightly upregulated in RTn and 3-fold in ’cortical focus’of WAG/Rij. Level of CACNA1H is also higher in both brain regions in WAG/Rij rats. CACNA1I showed insignificant decreasing in both studied tissues of WAG/Rij strain. Level of Cav 3.1 protein was increased in ’cortical focus’ tissue of WAG/Rij. We also demonstrated stable level of Kir 4.1 mRNA expression in ’cortical focus’. Our results may suggest CACNA1G involvement in SWD generation in somatosensory cortex while role of other T-type calcium channel subunits and Kir 4.1 is less possible.

Keywords

• childhood epilepsy
• low-voltage-activated calcium channels
• thalamus
• somatosensory cortex
• qPCR
• Western-blot analysis