Electrophysiology of the Somatic Muscles in the Nematode Ascaris lumbricoides

Chemistry and Neurophysiology

Weisblat, David Allan ; Strumwasser, Felix

University:California Institute of Technology

Department:Chemistry and Chemical Engineering

关键词: Chemistry and Neurophysiology;   

Others  :  https://thesis.library.caltech.edu/10032/1/Weisblat_DA_1976.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The electrical activity of the somatic muscles of theparasitic nematode Ascaris lumbricoides has been investigated.The functional muscle syncytium overlying the nerve cord ispreferentially excited by anodal stimulation with an extracellularelectrode. Cathodal stimulation preferentially excitesthe nerve cord, allowing determination of separateconduction velocities for the nerve cord and syncytium. Thepropagation velocity of the nerve cord is 16.2 ± 1.2 cm/sec;that of the syncytium varies with the calcium concentration,being 21.6 ± 1.3 cm/sec for unitary slow waves under normalconditions. Both values are too high to account for thepropagation of contractile waves in the intact animal.

Ascaris muscle gives rise to complex spontaneous depolarizationsconsisting of slow waves and graded spike potentials. Often, the spikes and slow waves are modulated intoperiodic bursts of electrical activity, which gives rise torhythmic contractions on a behaviorally significant timescale. Spikes appear to be mediated exclusively by calciumions the spike active potential varies with calcium concentration as expected for a calcium electrode and spikes persistin sodium-free media. Slow waves can be mediated byeither sodium or calcium ions; they persist when calcium orsodium are removed separately, but not when both are removedtogether.

In rhythmically active preparations, a burst of slowwaves and spikes accompanies each contraction. The modulationshows dorsal-ventral coordination if the right lateralline is intact, in accord with known nervous system asymmetry.Anterior-posterior coordination is also observed.