High perilymphatic potassium and rubidium levels modulate the sensory resting discharge in the isolated frog labyrinth.
The effects of high perilymphatic K+ and Rb+ concentrations (20 mM) on the posterior canal resting discharge have been examined in the isolated frog labyrinth. Both K+ and Rb+ produced an increase in spike frequency which is sustained by a parallel increase in the excitatory postsynaptic potential (EPSP) emission rate. High K+ and Rb+ levels reduce the size of the afferent spike, broaden its time course but do not induce repetitive activity at the axon level. The K+ and Rb+ facilitation proved to be inversely related to the fibre's initial resting activity. The facilitation produced by increased K+ was usually larger than that in Rb+ solution. High sensitive and low sensitive units with similar low resting discharge were detected in relation to their response either to K+ or Rb+. The effects of both ions can be explained on the basis of their interactions with the presynaptic hair cell currents.
Rossi
M L
ML
Istituto di Fisiologia Generale, Università di Ferrara, Italy.
Martini
M
M
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D007758:Ear, Inner / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology*; D011893:Rana esculenta; D012413:Rubidium / Q000494:pharmacology*
D012413:Rubidium; D011188:Potassium