Boldyriev O. Expression and function of the low threshold calcium channels in the thalamus and somatosensory cortex of rats in ontogenesis and under experimental absence epilepsy

Thesis is dedicated to comparative analysisofT-typeorlow-voltageactivatedcalciumchannels (LVACC) pore-forming alfa1-subunits (Cav3.1, Cav3.2andCav3.3) expressioninthalamic nuclei and somatosensory cortex on different ontogenesis stages and in absence epilepsy WAG/Rij rat model, search of possible gene expression regulators of these channels, and to matching between T-type currents and isoform mRNA expression in different thalamic neuron types. We designed a modification of single-cell RT-PCR technique for thalamic neurons which were distinguished by secreted neurotransmitter. By this technique we found in both inhibitory GABA-ergic and excitatory glutamate-ergic thalamic neurons express mRNA of Cav3.1, Cav3.2andCav3.3channels and moreover neurons majority expressed 2 or 3 isoform mRNAs simultaneously. T-currents differed insignificantly by their biophysical properties. We showed all 3 LVACC isoform expression in laterodorsal thalamic nucleus. Cav3.1 and Cav3.3 mRNA are expressed on comparable levels on 10th postnatal development day while Cav3.2 was much lower. On 25th day Cav3.1 and Cav3.2 mRNA quantity drop down dramatically but Cav3.3 stays on the same level. We demonstrated T-type channels alfa1-subunits mRNA level elevation in WAG/Rij rats primary epileptogenic region -somatosensory cortex of upper lip and vibrissae. There is 2,5-fold increasing of Cav3.1 mRNA quantity and 2,1-fold upregulation of channel protein compared to control Wistar strain. We were not able to register T-type calcium current in isolated cortical neurons of this region, possibly due to dendritic T-channel localization. There is Cav3.1 and Cav3.2 mRNA downregulation in laterodorsal thalamic nuclei of WAG/Rij rats found and 43% lower T-type current amplitude measured in neurons of this nucleus compared to ones of control Wistar rats. We determined microRNA rno-mir-1 as a potential Cav3.2 mRNA negative regulator in rat thalamus and brain cortex.