[Intracellular activity of potassium in frog spinal cord motor neurons]

Intracellular K activity (aik) in frog motoneurons of isolated spinal cord as measured by double-barrelled K+-selective microelectrodes revealed mean values as follows: 74.8 +/- 2.5 mM at the beginning of the recording and 51.6 +/- 2.9 mM afterwards (mean +/- SE). The average value of the resting potential of motoneurons (Em) was 54.1 +/- 1.2 mV. The difference between Ek (potassium equilibrium potential) and Em was 25.0 +/- 0.98 mV. Stimulation of ventral roots of spina-cord decreased aik both in normal and in Ca2+-free Ringer solution. No changes of aik occurred in synaptic stimulation without spike potentials.