Experimental diffusion models employed in this study. (A) Myocytes were patch-clamped close to one end, selecting myocytes 110–130 µm in length. In simulations, the concentrations of solutes within the pipette tip were constant. (B) Permeabilized or detergent/glycerol-extracted myocytes were aspirated rapidly into highly polished pipette tips with inner diameters of ∼12 µm. The restricted region, limiting conductance of the patch pipette, was estimated to be 10–25 µm long. (C and D) Gelatins and/or viscous polymer solutions were aspirated into pipette tips, and the limiting conductance was monitored during and after rapidly switching the pipette tip between solution streams of different compositions. Pipettes were employed with restrictions occurring over 20 μm (C) up to 300 μm (D). (E) 8-cm-long glass pipettes with a 1-mm inner diameter were carefully filled over 4 cm with one chosen solution, and the corresponding end was sealed with dental wax. Then, the second half of the pipette was filled with a second chosen solution, the corresponding end was also sealed with wax, and fluorescence profiles were acquired at chosen times as described in Materials and methods.