Figure 6

Effect of glutamate application on K⁺ fluxes. Glutamate (10 μM) was applied to cortical neurons following daily treatment with 1 μM Aβ_1-40, and to age-matched un-treated control cells. Peak values of K⁺ fluxes (A) and steady-state K⁺ fluxes recorded 20 min after glutamate application (B) are shown for one, three, six, and eight days of treatment with Aβ. Peak K⁺ efflux was substantially (1.6-fold) higher after one day of treatment with soluble Aβ_1-40 than in age-similar control cells and further increased to 5.7-fold difference after six days of treatment. The capacity of cortical neurons to retain K⁺ flux at pre-stress levels after glutamate challenge was assessed by comparing steady-state values of K⁺ fluxes 20 min post-treatment. K⁺ efflux in Aβ treated cells was significantly higher than in age-similar controls after treatment with Aβ suggesting that Aβ accumulation by neurons reduces their ability to maintain K⁺ homeostasis. * - P < 0.05, ** - P < 0.02, t-test. Error bars represent SEM (n = 4-7).