The Anomalous Spikes of Ascaris Esophageal Cells

The remarkable data by del Castillo and Morales (1967) on the eleetrophysiology of the Ascaris esophageal cell emphasize the usefulness of studies in primitive forms in which the record of evolutionary experimentation may still he preserved (Grundfest, 1959, 1963, 1964, 1966 a). They also present an interesting challenge to the ionic theory of bioelectrogenesis, requiring it to account for intracellularly recorded spikes that may result from electrogenesis that is diphasic or which is entirely hyperpolarizing. Obviously, if the theory can explain the new findings, it thereby gains new support. I propose to show that the modern ionic theory (Hodgkin and Katz, 1949; Hodgkin and Huxley, 1952) as extended to include the large variety of bioeleetric generators that are now known to exist (Grundfest, 1961, 1966 a, 1966 b) can, in fact, encompass these data. Since del Castillo and his colleagues have not yet completed their studies, only a partial theoretical interpretation can be given at this time and the specification of particular ionic processes remains only an assumption. However, even a preliminary analysis may prove useful in suggesting some desirable experimental approaches and in pointing up relationships of the new findings with observations on other electrically excitable electrogenie ceils. Markedly diphasic intracellularly recorded spikes have also been described in muscle fibers of the larval mealworm, Tenebrio molitor (Belton and Grundfest, 1962). In these cells it has been established that the hyperpolarizing component of the electrogenesis is due to K activation (Fig. 1 A) and it is probable, as del Castillo and Morales assume (p. 626) that the hyperpolarization of the "polarized" Ascaris cell is also due to K activation. The marked diphasieity of both cells thus is to be ascribed to the common factor; that the emf of the K battery (EK) is strongly negative to the resting potential (EM). The depolarizing component of the spike electrogenesis of Tenebrio muscle fibers is normally due to an inward current carried by Mg ++ (Belton and Grundfest, 1962), but other cations may be substituted for Mg ++ (Kusano and Grundfest, 1967, and unpublished data). As in other varieties of spikes, therefore, a negative slope characteristic is manifested as the membrane potential shifts from EM to Eg . In the Ascaris cell the nature of the cation involved in spike electrogenesis is as yet unspecified. During the subsequent K activation the membrane potential shifts from E9 to E~ in both cells. Since an outward current is associated with hyperpolarization the voltagecurrent characteristic has a second negative slope region. Finally, as the membrane potential approaches E~, K activation must be quenched. The inside negative charge