Imaging Dendritic Spines with Scanning Ion Conductance Microscopy (SICM)

The many practical difficulties of imaging small (~500nm) dendritic spine heads are discussed. A possible candidate for achieving this is presented, SICM. The drawbacks with the current operation of SICM are analysed, and suggestions for possible techniques to improve the process are looked at. In particular, mathematical models of the approach curve are analysed to give an estimate of the maximum height of the pipette above the cell giving acceptable resolution, ~80nm. It is also estimated that cell-pipette distances of more than 200nm give saturation of the current and no image information. A numerical method for calculating the expected current from a given pipette-cell configuration is developed, and its applications to improving imaging of spines discussed.