Changes of intracellular sodium and potassium ion concentrations in frog spinal motoneurons induced by repetitive synaptic stimulation.
A post-tetanic membrane hyperpolarization following repetitive neuronal activity is a commonly observed phenomenon in the isolated frog spinal cord as well as in neurons of other nervous tissues. We have now used double-barrelled Na+- and K+-ion-sensitive microelectrodes to measure the intracellular Na+- and K+-concentrations and also the extracellular K+-concentration of lumbar spinal motoneurons during and after repetitive stimulation of a dorsal root. The results show that the post-tetanic membrane hyperpolarization occurred at a time when the intracellular [Na+] reached its maximal value, intracellular [K+] had its lowest level and extracellular [K+] was still elevated. The hyperpolarization was blocked by ouabain and reduced by Li+. These data support the previous suggestion that an electrogenic Na+/K+ pump mode may be the mechanism underlying the post-tetanic membrane hyperpolarization.
D000818:Animals; D004553:Electric Conductivity; D004558:Electric Stimulation; D007425:Intracellular Membranes / Q000032:analysis* / Q000502:physiology; D009046:Motor Neurons / Q000032:analysis*; D011188:Potassium / Q000032:analysis*; D011893:Rana esculenta; D012964:Sodium / Q000032:analysis*; D013116:Spinal Cord / Q000166:cytology*; D013569:Synapses / Q000502:physiology*
D012964:Sodium; D011188:Potassium