Reversal potential of the end-plate currents and potassium feedback at the neuromuscular synapse.
The experiments were carried out at the neuromuscular junction of the frog. Erev of epc was estimated by two methods--extrapolation and interpolation. In K+-enriched solution Erev obtained by linear extrapolation from high-mp region changed according to the Takeuchi equation. The behavior of Erev obtained by interpolation was better described by the Goldman-Hodgkin-Katz equation. Under the change of the nerve stimulation frequency from 0.5 to 50/sec, the positive shift of Erev estimated by both methods was observed. This indicates K+ accumulation in active synaptic segments during activity. The elimination of the potassium current of epc by clamping of mp at the - 130 mV level resulted in the lowering of facilitation under paired nerve stimulation (20 msec interval) and in the decrease of the rate of facilitation under 50/sec frequency stimulation. The data support the presence of antidromic K+ action in the neuromuscular synapse.
D000818:Animals; D004558:Electric Stimulation; D007473:Ion Channels / Q000378:metabolism; D008564:Membrane Potentials; D009045:Motor Endplate / Q000502:physiology*; D009132:Muscles / Q000294:innervation; D009469:Neuromuscular Junction / Q000502:physiology*; D011896:Rana temporaria; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission
D007473:Ion Channels