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Ionic mechanisms of electrical activity in somatic muscle of the nematode Ascaris lumbricoides

Weisblat, David A. and Byerly, Lou and Russell, Richard L. (1976) Ionic mechanisms of electrical activity in somatic muscle of the nematode Ascaris lumbricoides. Journal of Comparative Physiology A, 111 (2). pp. 93-113. ISSN 0340-7594. doi:10.1007/bf00605526.

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The ionic dependence of the myogenic spike potentials and slow waves recorded fromAscaris lumbricoides somatic muscles has been investigated. Spikes appear to be mediated exclusively by calcium ions; the spike active potential varies with calcium concentration as expected for a calcium electrode and spikes persist in sodium-free media (Fig. 2). Slow waves can be mediated either by sodium or calcium; they persist when calcium or sodium are removed separately, but not when both are removed together (Figs. 3, 4, 6). In rhythmically active preparations, a burst of slow waves and spikes accompanies each contraction. Two phenomena may be related to the mechanism of this modulation: 1) TEA, although it does not prolong slow waves or spikes, induces rhythmic bursts of activity similar to spontaneous modulation (Fig. 5). This TEA-induced modulation appears to be myogenic. 2) Under conditions where calcium influx is reduced (either by addition of EGTA to the bath or by replacement of calcium with barium or strontium), very long-duration “square waves” are observed (Figs. 4. 7. 8). The square waves resemble slow waves in their ionic dependence, but differ in their sensitivity to TEA and to variation in the external potassium concentration. It is suggested that modulation and square waves involve the same channels. The significance of these results in understanding the role of myogenic activity in nematode locomotion is discussed.

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Additional Information:We thank Mr. Mac McGlaughlin for help in obtaining Ascaris. 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., by an NIH Traineeship on grant BCH Tol GM 01262-12 to D.A.W., and by an NIH Postdoctoral Fellowship (1 FO2 GM55347) to L.B.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
NIHNS 09654
NIH Predoctoral FellowshipGM 01262-12
NIH Postdoctoral Fellowship1 F02 GM55347
Issue or Number:2
Record Number:CaltechAUTHORS:20221004-680171300.3
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117233
Deposited By: Tony Diaz
Deposited On:12 Oct 2022 22:34
Last Modified:12 Oct 2022 22:34

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