[Quantitative determination of potassium content of spinal motor neurons frogs by x-ray microanalysis].

X-ray microanalysis has been made of the potassium content of motoneurons in the frogs Rana ridibunda and R. temporaria. The tissue was frozen in isopentane up to-160 degrees, dried in vacuum at-50 degrees, embedded into epoxy resin and sectioned by ultramicrotome. The obtained mean value of intracellular potassium concentration-65 mM/kg of wet weight or 80 mM/l of intracellular water-is in a good agreement with the results of calculation of intracellular potassium from equilibrium potential of post-spike after-hyperpolarization.