Effect of cortisol-induced inhibition of extraneuronal uptake on responses to isoprenaline in the kitten.

1. In anaesthetized kittens, cortisol (16 mg/kg) potentiated peak chronotropic responses to isoprenaline but did not affect peak bronchodilator responses to this amine. 2. In contrast, the duration of both chronotropic and bronchodilator effects of isoprenaline were clearly potentiated by cortisol. 3. These results have been linked with cortisol-induced inhibition of 3H-isoprenaline uptake in the perfused kitten heart and isolated tracheal smooth muscle.