The Response of the Ampullae of Lorenzini of Elasmobranchs to Electrical Stimulation

ABSTRACT The ampullae of Lorenzini are sensitive to weak electrical stimuli which presumably cause currents to flow along the jelly-filled tubes of the sense organ. Increase of the resting frequency occurs when the tube-opening is made negative to the capsule, and inhibition when the opening is positive, with opposite after-effects in each case. Adaptation is three-quarters complete in about 5 sec. When the stimulus is applied as a voltage gradient in the water overlying the ampullae, the threshold for the most sensitive units is 1 μV./cm., which represents a current along the tube of less than 5 ×10−11 A. When the stimulus is applied as a current directly to the tube opening, the threshold for the most sensitive units is 4 ×10−10 A. Changes in the salinity of the water at the tube opening are also effective, the threshold being about 3 %. Dilution causes excitation, and concentration causes inhibition. The response is not due to the osmotic differences, and so probably results from potentials established at the jelly-water interface.