Fig. 1.

TMA⁺ measurements and typical diffusion curves in control and APP23 mice. (a) A double-barreled TMA⁺-selective microelectrode (TMA⁺ ISM) and a micropipette for TMA⁺ iontophoresis were glued together with dental cement to stabilize the intertip distance at 100-150 μm, and this microelectrode array was introduced into the dorsal brain cortex. (b) Comparison of TMA⁺ diffusion curves obtained in 17- to 25-month-old transgenic and control mice. The diffusion parameters can be determined from the shape and magnitude of the curves. The ECS was larger, and ADC_TMA was lower, in APP23 animals than in controls. (c) ECS volume fraction (α) plotted against the depth of measurements (the zero level corresponds to the brain surface); α was changed in 17- to 25-month-old APP23 mice compared with age-matched controls.