The temperature dependence of conversion processes in the sensory organ of frog semicircular canals has been tested in the range 0-28 degrees C by recording the ampullar (Adc) and nerve (Ndc) slow potentials as well as the afferent discharge of impulses (Nfr) in the VIII nerve fibres. The results have shown that Adc is scarcely affected by temperature changes (Q10 less than 2) thus suggesting that stimulus conversion in labyrinthine cells does not imply chemical processes but mainly potassium conductance changes at their apical membrane. By converse, postsynaptic potentials and propagated spikes are markedly reduced at low temperatures (Q10 2.8 and 7 respectively) and only slightly increased between 20 and 28 degrees C. These observations are interpreted by considering the chemical nature of the processes which are involved. The temperature dependence in labyrinthine receptor activation is discussed in the view of its physiological meaning.
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