Propagation of electrical activity in the nerve cord and muscle syncytium of the nematodeAscaris lumbricoides

Summary The functional muscle syncytium overlying the nerve cord inAscaris lumbricoides is preferentially excited by anodal stimulation with an extracellular electrode. Cathodal stimulation preferentially excites the nerve cord, allowing determination of separate conduction velocities for the nerve cord and syncytium. The propagation velocity of the nerve cord is 16.2±1.2 cm/s; that of the syncytium varies with Ca²⁺ concentration, being 21.6±1.3 cm/s under normal conditions (Figs. 5, 6). Both values are too high to account for the propagation of contractile waves in the intact animal.Modulation of spontaneous electrical activity on a behaviorally significant time scale is observed. The modulation shows dorsal-ventral coordination if the right lateral line is intact, in accord with known nervous system asymmetry (Fig. 10).We thank Mac McGlaughlin for help in obtainingAscaris, Professor Felix Strumwasser for the loan of the CAT, and Dr. Lou Byerly for assistance in statistical analysis and in the design of the trigger circuit. This work was supported by a Sloan Foundation Grant in Neuroscience and a U.S. Public Health Service Grant (NS 09654) to R.L.R., and by a N.I.H. Traineeship on Grant BCH 5 Tol GM 01262-12 to D.A.W.