Dysregulation of GABAergic System in the Inferior Colliculi of Rats during the Development of Audiogenic Epilepsy

Abstract

Epilepsy is tightly associated with dysfunction of inhibitory GABA neurotransmission. In this study, Krushinsky–Molodkina (KM) rats genetically prone to audiogenic seizures (AGS) were used. KM rats are characterized by the development of audiogenic epilepsy during postnatal ontogenesis, with AGS onset at the age of 1.5–2 months and fully developed AGS expression by 3rd month. We analyzed GABAergic system of the inferior colliculi (IC) of KM rats at different stages of postnatal development. Wistar rats were used as a control. In the IC of young KM rats, Na+/K+/Cl– cotransporter 1 (NKCC1) expression was increased, while K+/Cl– cotransporter 2 (KCC2) was unchanged indicating impairment of postsynaptic GABA action at early stages of postnatal development. Moreover, we revealed also an increase in the expression of vesicular GABA transporter (VGAT) in the IC which additionally pointed on the higher activity of GABA release. In adult rats, in opposite, we revealed a decrease in the expression of KCC2 transporter indicating downregulation of GABA inhibition on the target cells. Thus, GABA dysregulation in the IC can mediate the seizure susceptibility in adult KM rats.