Localization of a Microelectrode Tip in Muscle Cell

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Abstract
A method is described for accurate localisation of a recording glass microelectrode in muscle cell and subsequent histochemical staining of the myoneural junction of the cell with cholinesterase and, finally, for localisation of the recording site itself in an electronmicroscopic picture. Microelectrodes were filled with 1.1 M of K4Fe(CN)6 and 1.5 M of Na2HPO4. With the microelectrode at the recording point, a 1: 1 mixture of 0.1 M of Pb(NO3)2 and 5 per cent acetate‐buffered (pH 5.6) glutaraldehyde was applied to its environment and anions were driven electrophoretically from the microelectrode with a DC of about 2 μA for 5–10 sec. into the muscle cell. The white sediment that originated was turned dark with 1 per cent (NH4)2S. The size of the sediment was 5–20 μ. It was seen clearly under the light microscope. This method did not affect the histochemical stainability of the motor end‐plate. As the sediment contained heavy metals it was visualised also in the electron microscopic picture after further fixation for one hour in buffered glutaraldehyde. The sediment was visible also in the Epon resin block and this helped the trimming of the specimen. The sediment consisted in a normal electron microscopic picture of rough heavy‐metal grains.
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