Differential thermosensitivity and electric prepolarization of the ampullae of Lorenzini

In a single-fibre preparations the afferent discharges from prepolarized ampullae of Lorenzini responding to graded temperature steps were investigated in the dogfish (Scyliorhinus canicula). The transformation characteristics of the ampullary receptors, especially their differential thermosensitivity interfering with electrosensitivity, were analyzed. Prepolarization significantly influenced the dynamic component of differential thermosensitivity, while the static component remained practically unchanged. Hyperpolarization reduced positive and negative dynamic thermal responses; depolarization amplified them. Biological consequences of this bimodal interference for receptor transformation of superimposed thermal and electric stimuli and for decoding afferent ampullary impulse patterns are discussed.