Elevate concentrazioni extracellulari di potassio e rubidio modulano la trasmissione sinaptica nel labirinto di rana

High extracellular K or Rb levels (20 mM) produce an increase in the resting EPSP and spike frequencies recorded intra cellularly from single fibres of the posterior nerve in the isolated frog labyrinth. The afferent discharge facilitation proved to be inversely related to the fibre's initial resting activity. The K effect is systematically larger than the Rb effect. High sensitive and scarcely sensitive units may be identified with respect to K and Rb action. The present findings suggest that, according to previous models of hair celi functioning, the K and Rb effects are mediated by a raise in intracellular Ca concentration which sustains an increased transmitter release at the cyto-neural junction