| Abstract: | Intracellular microelectrodes were used to measure resting and action potentials of electric eel electroplax cells from which the middle portion of the anterior moiety had been removed. External electrode studies of this preparation have been described by Chagas and Esquibel (C. R. Acad. Sc., Paris, 260: 3172 ('65)). In the present studies it was found that the resting and action potentials were almost as large as normal in the intact portion of the preparation, whereas these potentials were greatly reduced in the areas from which the anterior moiety had been removed. The reduction in amplitude was greater the farther the microelectrode was from the intact portion, indicating the possibility of decremental spread from the intact portions. The action potentials measured with external electrodes appeared to be an average of potentials from the various areas of the preparation. In other experiments the entire anterior moiety of the electroplax was removed, leaving only the innervated plasma membrane plus some adhering cytoplasm and extracellular material. Various high K+ solutions were used to bathe the inner surface. No action potentials could be elicited from these preparations, but resting potentials as high as 51 mV were observed using external electrodes. The resting potential could be reduced reversibly by carbamylcholine applied to the outer surface. Carbamylcholine applied to the inner surface had no effect. |
