K+-DEPOLARIZATION - AN ALTERNATIVE METHOD OF INHIBITING EXTRANEURONAL UPTAKE ON ISOLATED TISSUE PREPARATIONS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 243  (2) , 209-216
Abstract
Responses to isoprenaline were not potentiated by extraneuronal uptake (ENU) inhibitor drugs (phenoxybenzamine and metanephrine) in preparations of guinea pig uterus which were contracted by K+-Krebs solution. Fluorescence histochemical experiments demonstrated that isoprenaline could accumulate extraneuronally in uterine smooth muscle and that this accumulation was inhibited by phenoxybenzamine and metanephrine. Accumulation was inhibited by K+-Krebs solution. The failure of ENU inhibitor drugs to potentiate isoprenaline responses on K+-depolarized uterine preparations might occur because the uptake mechanism was inhibited by the K+-Krebs solution. Support for this hypothesis was obtained from experiments on guinea pig tracheal preparations in which ENU inhibitor drugs potentiated isoprenaline responses. In K+-depolarized tracheal preparations this potentiation did not occur presumably because the K+-Krebs solution inhibited the uptake. K+-depolarization of a tissue may provide an alternative to the use of extraneuronal uptake inhibitor drugs when it is necessary to eliminate this site of loss in quantitative studies on .beta.-adrenoceptors in isolated tissues.

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