Transepithelial potential in Malpighian tubules of Rhodnius prolixus: lumen-negative voltages and the triphasic response to serotonin

Previous studies of the Malpighian tubules of Rhodnius reported lumen-negative values of transepithelial potential (TEP), and a characteristic triphasic change in TEP in response to stimulation of tubule fluid secretion by serotonin. TEP was measured using the Ramsay technique, in which electrodes are positioned in bathing and secreted fluid droplets for tubules isolated under paraffin oil. The validity of this method of TEP measurement has …