IC50: 5.7±2.1 µM (Na + /Ca 2+ exchanger)
KB-R7943 mesylate blocks NMDAR-mediated ion currents, and inhibits NMDA-induced increase in cytosolic Ca 2+ with IC 50 =13.4±3.6 µM but accelerates calcium deregulation and mitochondrial depolarization in glutamate-treated neurons. KB-R7943 depolarizes mitochondria in a Ca 2+ -independent manner. KB-R7943 inhibits 2,4-dinitrophenol-stimulated respiration of cultured neurons with IC 50 =11.4±2.4 µM. In addition to NCX rev , KB-R7943 dose-dependently and reversibly blocked ion currents elicited by NMDA. KB-R7943 dose-dependently inhibits NMDA-induced increases in [Ca 2+ ] c with IC 50 =13.4±3.6 µM confirming the inhibition of NMDA receptors observed in electrophysiological experiments. wt RyR1-HEK 293 pretreated with KB-R7943 (10 μM, 10 min) dissolved in the bulk perfusion exhibited significantly attenuated responses to caffeine. In this regard, KB-R7943 produced more pronounced inhibition of caffeine-induced Ca 2+ release elicited by 1 mM compared with 0.5 and 0.75 mM (60 versus 58 versus 37%, p<0.05, respectively). KB-R7943 inhibits both I hERG and native I Kr rapidly on membrane depolarization with IC 50 values of ~89 and ~120 nM, respectively, for current tails at −40 mV following depolarizing voltage commands to +20 mV. I hERG inhibition by KB-R7943 exhibits both time- and voltage-dependence but shows no preference for inactivated over activated channels.