Membrane permeability changes during stimulation of isolated salivary glands of Calliphora by 5-hydroxytryptamine

1. The membrane resistance of isolated salivary glands was found to decrease in response to 5-HT. The change in resistance was calcium-dependent. 2. The resistance change of the apical membrane was found to be much greater than the change in resistance of the basal membrane. 3. Potential responses under current-clamped conditions showed that one part of the biphasic response to 5-HT (attributed to an increase in chloride permeability) could be reversed and the other part (attributed to an increase in a potassium pump) could not. 4. These observations have been incorporated into a model which, on evaluation, predicts all of the observed potential changes during the action of 5-HT. It suggests that the potential responses reflect changes in the internal chloride concentration produced by the calcium-dependent increases in chloride permeability.