Expression of genes of KCNQ potassium channels in cultured hippocampal inhibitory interneurons, and participation of these channels in the regulation of GABA-ergic transmission

Abstract

The expression and functioning of KCNQ potassium channels in the membranes of inhibitory interneurons of hippocampal culture and the involvement of these channels in the regulation of GABA-ergic synaptic transmission were investigated using a reverse transcription (RT) and polymerase chain reaction (PCR) for the single-cell technique (single-cell RT-PCR) and a patch-clamp technique in the "whole-cell" configuration. Expression of the genes of KCNQ2 and KCNQ3 α-subunits was revealed in all the GABA-ergic interneurons studied. A small level of the KCNQ5 subunit expression was detected in 38% of the cells. Activation of the somatic KCNQ channels of interneurons led to a shift in the resting potential toward more negative values, and also to the inability of these cells to generate spike series in response to prolonged depolarizing current injection. Functional KCNQ channels were also revealed in axons of inhibitory interneurons. Activation of these channels in the axons inhibited spike generation; this led to a decrease in GABA release from the terminals and, accordingly, to suppression of inhibitory synaptic responses in postsynaptic neurons.