Figure 2.
Effects of Na+,K+-ATPase inhibition with 5 μM dihydro-ouabain, DHO (A) and K+ channel inhibition with 200 mM Ba2+(B) on baseline extracellular K+ concentration, average recovery rate during stimulation and undershoot in hippocampal brain slice experiments like that shown in Figure 1. Both DHO and Ba2+ cause an increase in baseline, DHO reduces recovery rate drastically, but Ba2+ has no effect (P = 0.99 for this effect but <0.01 for all others), and the undershoot is almost abolished by DHO, but increased by Ba2+. The effects are consistent with profound Na+,K+-ATPase involvement in maintenance of a normal baseline, recovery after stimulation-induced K+ increase and undershoot, and no K+ channel-mediated contribution to recovery. As suggested by the authors, the Ba2+ effect on the undershoot suggests that outward directed K+ channel-mediated K+ transport diminishes the undershoot. The increased baseline concentration might suggest a less efficient spatial redistribution of K+. From D'Ambrosio et al. (2002).