Fig. 8. Inhibition of K⁺-sensitive luminescence by Ruthenium Red. The integrated response to [K⁺] over 200 s was normalized to total luminescent capacity (K⁺-SL/TLC) for each sample to compensate for modest decrease of apparent TLC after Ruthenium Red treatment (N=4-10 for each treatment/stimulus combination tested). Values are means ± S.D. Treatment for >4 h with 50 µmol l^-1 Ruthenium Red inhibited stimulation by added solutions containing low to moderate [K⁺] but not high [K⁺].