Figure 1.

Performance of transporters and recovery of the receptor function. Neuronal [Cl⁻]_i is maintained mainly by neutral active CCCs (KCC2 and NKCC1), and less by Cl⁻ channels (SLC26 family) and exchangers (SLC4 family—AE3, NCBE or NDCBE). CCCs move the Cl⁻ ions by utilizing the energy electrochemical Na⁺ and K⁺ gradient, whose maintenance involves Na⁺, K⁺ATPase. CCCs need at least 5 min to recover [Cl⁻]_i [48,57,68,69,70,71], while the GABA_AR-mediated conductance may recover during approximately 10–15 s after [Cl⁻]_i changes [51,61]. After purification and reconstitution into proteoliposomes, the β3-containing GABA_AR homopentamer participates in ATP-consuming Cl⁻ transport for a short period (~30 s) and then reaches a plateau [35]. The bottom panel shows the changes of [Cl⁻]_i after application of Mg²⁺-ATP in the experimental medium containing proteoliposomes with embedded GABA_AR/Cl⁻, HCO₃⁻ATPase, as well as the fluorescent dye for chloride.